Coin of the ancient Greeks of the colony of Byzantion
symbol survived through the centuries and became the flag of modern Turkey
The ancient Greeks started everything!
Wednesday, May 28, 2014
Wednesday, May 21, 2014
Ashern: Drifting of Continents
COURSE OUTLINE
CONTINENTS ADRIFT June 2014, Ashern
Notes
& videos
TOPICS TESTS/ PROJECT
Week 1 Outline / summary
--------
Great Meteor hotspot
Yellowstone hotspot
Week 2
MacKenzie dike swarm
test 25 %
Reunion hotspot
Paleomagnetism
Deccan Traps & death of dinosaurs
Siberian
Traps & Permian Death
Zealandia
The supercontinent cycle
The Gypsumville crater
The supercontinent cycle
The Gypsumville crater
Week 3 Story
of Geology: J. Hutton test
25 %
Supervolcanoes: Toba Project
due - 25 %
Afar new ocean
Submarine volcanoes
Kamchatka, Russia
Week 4 Presentations Final 25 %
Popigai Crater, Siberia ( diamonds)
Super Comet. After the Impact (Discovery ch.)
Field trip to Gypsumville crater
Popigai Crater, Siberia ( diamonds)
Super Comet. After the Impact (Discovery ch.)
Field trip to Gypsumville crater
PROJECT : up to 4 pages, topic relevant to
course. Include facts & useful information
to know.
Some topic that can be
presented to school class to remember
Summary of previous knowledge
•Continental drift
(movement of continents)
•Seen by many
observers, but documented by Alfred Wegener in early 1900’s
•Torontonian Tuzo
Wilson contributed also
•Sea floor spreading
(oceans get larger)
•Convection currents
bring heat (magma) to the surface
•Ocean floor like a
conveyor belt
Topics
•The interior of the
Earth
•Continental Drift
•Ocean ridges
•Continental Rifts
(East African Rift)
•Continental
transforms (St. Andreas Fault)
•Subduction zones
•Orogenic belts (mountains)
•The Supercontinent
cycle
•Some results: ocean
circulation, weather, mineral deposits
Earth’s Interior
•All information from
the study of seismic waves
•At about 40 km below
surface Mohorovicic discovered there is an abrupt change in velocity from 5
km/sec to 8 km/sec
•That is the bottom of
the crust and the top of the mantle (the Moho)
•At a depth of 2900 km
the velocity drops, therefore the upper core is liquid. But at 5100 km the
velocity increases abruptly, that means the inner core is solid
Heat in the Interior- makes everything move
•Tremendous heat moves
slowly upwards by convection currents
•Some hot areas or
plumes of heat arrive at the surface in the form of molten rock plus gases and
metals
•This volcano would be
a mid-ocean ridge, an isolated volcano from a subduction zone on
the ocean floor/land or a hotspot
Under the oceans
•Average water depth
of 4 km
•Crust averages 5 km
thick
Crust
•On continents it can
be as old as 4 b.y.
•In the oceans the
oldest is 180 m.y. and it is progressively increasing in age from the oceanic
ridges
•Oceans are therefore
viewed as transient features of the Earth’s surface
•50 % of the surface
area of the ocean floor has been created during the last 65 m.y.
Tectonic activity
•Continental crust
extensively folded and faulted with evidence of multiple tectonic events
•Oceanic crust,
however, is much more stable and has suffered little deformation except at
plate margins
Igneous activity
•Very few volcanoes on
continental crust
•Only activity along
mountain belts of Andean type
•Within the oceans
much greater activity (volcanic & intrusive), mostly ocean ridges and
island arcs. Oceanic islands, however, have much less igneous activity
Topic for investigation in this course
•Hot spots and
movement of plates over them
•Plate can be oceanic
or continental
•Result would be a
linear arrangement of volcanoes
Major Igneous provinces - picture
Hot spots - picture
Hot spots (Foulger, 2010) - picture
Best example : Hawaii – Emperor seamount
chain - picture
Hawaii
– Emperor seamount chain
•At least 80 volcanoes
stretching over 5,800 km
•Going back to 85 m.y.
ago
•Many atolls (the most
northerly)
•The pronounced “bend”
in trend not due to change in plate motion but to change in the direction of
heat flow from the mantle (“mantle wind”) acc. to recent research
Stages in sea
volcanoes
•From submarine
eruption to volcanic shield stage
•Erosional stage,
volcano breaks down to sea level, corals form a reef (atoll). When island moves
too north for corals to survive, the reef dies and weathering brings it
underwater
•Guyot stage:
flat-topped seamount below sea level
Hotspot volcanic chains
•Hawaii – Emperor
seamount chain
•Louisville seamount
chain
•Walvis Ridge (Gough
& Tristan hotspot)
•Kodiak – Bowie
seamount chain
•Cobb – Eickelberg
seamount chain
•New England seamount
chain
•Anahim volcanic belt
•Mackenzie dike swarm
•St. Helena seamount
chain
•Cameroon volcanic
line
•Southern Mascarene
plateau (Reunion)
•Ninety East ridge
•Tuamotu
Austral Gilbert
Juan Fernandez ridge
Plus
•A long list of (~ 60)
volcanic islands & land volcanoes that are postulated to be hot spots, too
•Examples: Azores,
Canary, Afar, Yellowstone, Galapagos, St. Helena, etc
Example from N.
America
•The North American
plate has been / is moving westwards
•Hot spots are
stationary
•Arrival of heat at
the surface in the form of a line of volcanoes (as the plate is moving)
Great Meteor or New England
hotspot track
hotspot track
•A vast trail of
hotspot magmatism
•Over 5,800 km long
•From Nunavut to middle
of Atlantic ocean
•Oldest magmatic
activity 214 + m.y old
•One of the oldest
hotspot tracks on Earth
•Over 80 volcanoes,
most under the sea
•Seamounts easily
visible on relief maps of the ocean
Visible in the
Atlantic ocean - picture
The Bear guyot
(flat-topped seamount) – picture
Great
Meteor hotspot track
•NWT/Nunavut
kimberlites
•Churchill (Nun.)
kimberlite 214 –
192 m.y.
•Attawapiskat (Ont.)
kimberlites
180 m.y.
•Kirkland Lake (Ont.)
kimberlite 165 – 152 m.y.
•Lake Timiskaming (Ont.)
kimberlites 155-134my
•Monteregian Hills
(Que.)
140 - 118 m.y.
•White Mountains
(N.H.)
109 m.y.
•New England
seamounts
100 – 10 m.y.
Kimberlites in Canada
– map
Information on
diamonds
•Diamonds is a
relatively new discovery in Canada (1991)
•Used to come just
from South Africa
•Found in explosive
volcanoes within a rock called kimberlite
•It is like a circular
pipe going into earth with a shape like a carrot
•On the surface about
1 km across
Kimberlites
•Rock is a magma
coming from the mantle
•Very unusual rock
•Lots of olivine and
exotic minerals like garnet, spinel, pyrope & diopside
•The rock is magnetic
rock due to abundant magnetite
•Can be picked up by a
magnetometer survey, ground or airborne
•However, the target
is small
•Diamonds are created
at 150 km depth
•Magma just brings
them to the surface
•Magma is from mantle
and the volcano is very explosive
•On the surface
olivine frequently gets altered into soft peridotite that weathers into blue
clay
Discovery of diamonds
in Canada
•1st
diamond found while panning for gold in Yukon (diamond is relatively heavy)
•Yukon geology has
been studied in detail and there are no diamond-bearing rocks there
•A geologist argued
that it had been transported by glaciers
•He tried to trace it
up – ice
•In that area the ice
moved from east to west
•Therefore, the
diamond must have come with the glacier from the east
•Looking for diamonds
in the overburden would be impossible because it is so rare
•He decided that other
minerals which are more common than diamond must have come with the diamond as
well
•After taking numerous
overburden samples he decided that several minerals accompanied the
diamond-bearing rock
“Indicator minerals”
•Are rich in chromium
and titanium that makes them very bright in color
•Red garnets
•Green pyropes
•Red spinel
•Green diopside
•All can be identified
in overburden (soil) by experts
Follow the indicator
minerals up-ice
•He started sampling
river sands from Yukon and 25 years later arrived in Nunavut!
•Next set of samples
had NO indicator minerals
•That means he had
passed over the source of the anomalies
•Simple magnetic
survey located the magnetite-rich, diamond-bearing kimberlite
•This was the 1st
diamond discovery in Canada
Kimberlites
Part of the Great
Meteor hotspot track that appears to start in Nunavut and continues SE to the
Atlantic ocean
Why kimberlite magma
there?
•Opening of the crust
facilitated by previous large scale eruption of the MacKenzie Dike Swarm &
the Matachewan Dikes that “stretched” the ground and prepared it for a later
intrusion of magma from great depth
First diamond
discovery in 1991
•By Dia Met in the Lac
de Gras area
•First diamond mine in
1998 (Ekati)
•Several diamond mines
produced diamonds since 1998
Kimberlite pipe –
picture
Mine claims stretch NW
to SE – map of parts of NWT/Nunavut
Some diamond
properties – picture/map
Three pipes – picture
from the air
Diamond crystals: 8
& 12-sided – picture
Colored diamonds are
rare (bluish) – picture
but very pricy (pink)
– picture
kimberlite – picture
of rock
The “spots” are
minerals, or parts of wallrock that fell into magma – two pictures of
kimberlite
Churchill Kimberlite Field
•North of Churchill,
Man.
•Formed during
magmatic events from 225 m.y. to 170 m.y. ago
•No producing mines
yet
Known kimberlite pipes
(78) – map of part of Nunavut
Attawapiskat kimberlite field
•Two pipes 90 km west
of Attawapiskat, Ontario
•170 m.y. old
Victor mine by DeBeers
– map of Ontario with location of mine
Lake Timiskaming kimberlite field
•Canada’s most
southerly kimberlite field
•Contains over 50
kimberlite pipes some of which are diamond-bearing
•Numerous in the
Kirkland Lake area
•Formed 147 m.y. ago
•NE Ontario &
adjacent NW Quebec
•No producing mines
yet
Migration of the
hotspot – map of NE Canada
“Mountains” near
Montreal, Que. – 3 pictures taken from the air
Monteregian Hills
•Name Height Age
Location
The Monteregian Hills
•Linear chain of
isolated hills
•Prominent scenery
•Mount Royal (or
Montreal) is one of them
•Each hill is an
eroded Cretaceous age intrusive igneous rock, prob. an active volcano around
125 m.y. ago
•To the west no
volcanoes: probably magma could not come through because crust too thick
Why hills ?
•Igneous rock is more
resistant to erosion than surrounding sedimentary rocks (mostly limestone)
several pictures from the McGill university
museum about these hills
Train tunnel under Mt.
Royal - picture
Rock types making up
the hills – picture
Sections of hills – 3
pictures
Dark, mafic-rich
volcanic/intrusive rock – 2 pictures from landscaping at a Montreal hospital
Dark intrusive rock
cutting across light colored limestone – picture
White Mountains
•Cover a ¼ of the
state of New Hampshire
•Part of the northern
Appalachians
•The most rugged
mountains in New England
•Most famous is the
1,917m Mt. Washington, the highest peak in NE USA
•Used to hold the
record for fastest wind (372 km/hr)
map of NE Appalachians
painting of the White Mountains – picture
•Origin of the “White”
unsure
•Maybe the snow at the
top or the white mica of the granite at the summit
•Igneous intrusions
formed the mountain 124 to 100 m.y ago
•First seamount (Bear)
formed 103-100 m.y. ago
•Last seamount
(Nashville) 83 m.y. ago
Continuation of hotspot in the ocean
•Called the New
England seamount chain
•Over 1000 km long
from the Massachusetts coast
•Over 20 extinct
volcanoes rising up to 4,000m from the ocean floor
•The longest seamount
chain in the N. Atlantic
•Attached to them are
diverse fauna
2 pictures showing individual seamounts and
hotspot track under ocean
Corner Rise seamounts – relief map of N. Atlantic
•A chain of extinct
submarine volcanoes east of the New England seamount chain
•In 2007 deep fishing
trawlers caused considerable damage to corals atop two undersea mountains
•All bottom-living
animals killed
•Deep sea fishing
still not regulated, UN scientists did not reach consensus
Relief map with
elevation contours – picture
Seawarte seamounts
•As the Atlantic
continued to spread, the hotspot “jumped” east of the mid-ocean ridge to form
the Great Meteor seamount (also called tablemount) south of the Azores
•The New England
seamounts were once at or above sea level. As they moved away from the hotspot,
lava cooled and contracted (plus erosion) sinking back down into the ocean
•The peaks are now
about a km below sea level
relief map of the Great Meteor guyot –
picture
Newfoundland seamounts
•Off Newfoundland
•An age of 97 m.y.
obtained for one of them
•Probably formed by
the Azores hotspot
undersea map of seamounts – picture
VIDEO : Continents Adrift (duration 26.06 min
VIDEO : Continents Adrift (duration 26.06 min
•Wegener’s Pangea theory with some
evidence
•Real evidence came
much later from the ocean floor
•Sea-floor spreading
shown by students
•“connect-the-dots” of
earthquakes mark plate boundaries
•Hot spot models
•Use towels on a table
to demonstrate how mountains form
Yellowstone
hotspot
•Currently lies under
the caldera
•Most recent
super-eruption took place 640,000 years ago and created the Yellowstone caldera
•One of the most
geologically dynamic places on earth due to the shallow source of magma
•Contains ~ 50% of the
world’s hydrothermal features such as geysers, hot springs, mudpots &
fumaroles
•Hydrothermal systems
due to shallow magma & abundant source of water from snow that percolates,
is heated up, boils or is superheated and rises
•It dissolves the
rhyolite and dissolved silica precipitates along cracks in the earth or as
siliceous sinter around vents on the surface
White siliceous sinter
around vents – picture of geysers
Bubbling mudpots –
picture
The caldera – picture
Tremendous size!
•Elevation of caldera
3,142 m
•Last eruption was
1,350 BC
•Caldera is 55 km by
72 km
•Size of magma chamber
is 80 km long, 40 km wide and 8 km deep
•It holds 25,000 km3
of magma (if full)
Section of caldera –
drawing
Earthquakes to the NW
– picture
Section of mountain –
conventional drawing
Research
•Change in ground
elevation
•Records of
earthquakes studied to decipher structure of interior
•Local earthquakes
triggered by distant quakes, example the 1964 & 2002 Alaskan earthquakes
Heat from 60 km depth?
– drawing
Plume towards the NW –
drawing
Heat in the interior:
with help from seismic waves
Uplift & subsidence
– picture
The 2002 Denali 7.9
earthquake (Alaska) – map
Eruption volumes –
drawing
Migration of hotspot -
map
Migration of caldera
& deposits - map
Tail of plume – map
Stresses in the area –
map
Last 3 eruptions – map
Extent of deposits of
last 3 eruptions – map
Timeline of volcanism –
world map
VIDEO: Yellowstone, the biggest eruption ever awaits mankind (duration 44.59 min)
Week 3
Contents
•Story of geology: James Hutton (video)
•Supervolcanoes :Toba (video)
•Afar new ocean / East African Rift (video)
•Submarine volcanoes
•Kamchatka peninsula (video)
Video: The story of Geology, James Hutton
•BBC Men of Rock part 1 (59.00)
•The contribution of James Hutton, a doctor in Scotland who loved to debate
•People wondered about the Earth, how old it was
•He observed erosion while working in a farm
•Didn’t believe in literal interpretation of Bible
•His friend James Watt invented the “steam engine” (not steam power) that resembles the earth’s interior
•Volcanoes are like giant heat furnaces (where steam is generated)
•He was a genius: he could make connections between events
•An accident at a glass factory taught him a lot how molten glass (magma) cools
•His presentation to the Royal Society was rejected prob. because he was lacking in evidence – the only geology text at the time was the Bible
•His theory advanced when he found an outcrop of granite intruding sediments
•Difficult for people to believe without this evidence
•60 years later pompous Lord Kelvin rejected Hutton’s theories, but he contributed by estimating age of the earth from time to cool a molten globe (20-40 m.y.). No one believed him either
•Hutton’s unconformity at Siccar Point however, became a world monument
•The discovery of radioactivity in 1898 proved that Hutton’s theory was correct
•The age of rock comes from crystals of zircon after measuring the uranium / lead ratio inside this mineral
•The age of Scotland oldest rocks came to be 2.6 – 3.0 b.y.
Unconformity at Siccar Point, Scotland
Supervolcanoes
•The story of Toba
Video: Mystery of the megavolcano
•Research for 15 years started with samples of ash at the bottom of the ocean: from a volcano but which one?
•Independent research by two others on other topics
•1st clue: Greenland in 1988 Zielinski studied composition of the atmosphere. He found an unusual abrupt anomaly 75,000 years ago with a sulfate content 40 times the normal
•Must have been a thick blanket of sulfuric acid droplets in the air
•2nd clue: Rampino studied oxygen atoms in shells of sea-bottom forams to measure temperature. He came across an abrupt anomaly of a 5 degrees C drop in temp. some 75,000 years ago. That was a catastrophic event like an ice age
•3rd clue: Other researchers were studying the depth of water in Lake Toba. It was very deep, like a big hole and all around the lake were thick deposits of igneous rock from magma. Ash samples matched ash found at sea bottom in the ocean and both were 75,000 years old
•There is subduction under Lake Toba, some 30 km below surface
•Huge reservoir of magma
•“Supervolcano”: at least 1,000 km3 of ejecta
•A 2 km deep hole after explosion was filled by rainwater
•NASA simulation of eruption. Sulfuric acid cloud can turn planet into Ice Age; plants die, animals & humans starve (60 % of humans died), forams die in the ocean
Supervolcano
•Term not used in scientific work until recently
•Due to large amount of lava and gases it can cause dramatic change in the weather & extinctions
•It can be two types: large igneous provinces & massive eruptions
•Can form at a hotspot (Yellowstone) or at subduction areas (Toba)
Afar: new ocean is born
•A triple junction of plates (also a hotspot)
•Part of East African Rift
•Rifting started 25 m.y. ago (Red Sea 30 m.y.)
•Behaves like a mid-ocean rift, but started as continental flood basalts in several places (Ethiopia, Somalia & Kenya). Continued as rifting with magmatism along the entire rift system
•Reactivation of old faults and development of new normal faults typical of all rifts
•Not all volcanoes are equally active
•Many volcanoes were created by the rift, but not all of them lie along the rift today
•The Lengai volcano is the only natrocarbonatite volcano in the world. It has no silica, crystallizes in midair and shatters like glass!
•The rift system is the largest seismically rift on Earth today. Strongest quake was 7
•A significant source of early human fossils
•The rapidly eroding highlands quickly filled valleys with sediments, thus easy to preserve remains
Erta Ale, Ethiopia
•A continuously active basalt (like ocean) shield volcano
•Surrounding area below sea level
•Has the longest-existing lava lake
•Volcano over the East African Rift system
•Not studied much as terrain most inhospitable –very hot, salty desert, even Afar people are vicious to strangers
Video: Erta Ale, Ethiopia
•Part of the East African Rift
•Sulfuric acid pools – the acid cooks food like a microwave oven
•Pools may also contain extremophiles which can be used to fight diseases
•The pH of the pools is below zero! Extreme!
•That means magma is just below
Active rifting
•Fissure opened up a few years ago
•Soil temp. up to 97 degrees C
•Gases escape, esp. deadly H2S
Lava lake
•One of 4 in the world
•This is the oldest
•Volcano has 2 craters
Submarine volcanoes
•The most productive volcanic systems on Earth are hidden under an average 2.6 km of water
•Mid-ocean ridges produce an estimated 75% of the annual output of magma
•The magma & lava create the edges of new oceanic plates and supply heat & chemicals to some of Earth’s ecosystems
•They produce life & metals
•There are over a million submarine volcanoes
•Perhaps 75,000 of these rise over 1km above the ocean floor
Kamchatka, Russia
Almost like a volcanic island
•Is a World Heritage Site
•Has endemic plants and other unique animals/plants
•11 species of salmon co-exist
•Surrounded by water that does not freeze & has relatively mild climate
•One of the most volatile (volcanically) regions on Earth
•Video: Smoking beauties, Kamchatka (25.50)
•29 active volcanoes (300 total)
•You can take an arduous trip to see them
•Volcanic glass, sharp rocks, steep slopes, up to 3 km high
•Very explosive volcanoes (rich in silica), gases could not escape through lava
•Volcanic bombs, dust, mudpots
•Rocks rich in sulfur, copper, iron
•900 degrees C in fractures, put your stick in & will catch fire instantly
•Terrain was test ground for lunar vehicles
•Climbers have to keep constant pace for easier breathing
•“Valley of geysers”, 2nd biggest after Yellowstone
•City of Petropavlovsk has 2 volcanoes behind it
several pictures of volcanoes, geysers, mud pools of Kamchatka peninsula
Uzon caldera
Several pictures with CO2 gas bubbles, geysers & hot pools
week 4
Presentations
Field Trip to the Gypsumville Meteorite Crater
shatter cone (?) from the Gypsumville meteorite crater
VIDEO: Yellowstone, the biggest eruption ever awaits mankind (duration 44.59 min)
•Magma chamber only 8
km below
•Several super
eruptions of ash happened before
•Caldera is collapsed
volcano after last eruption
•Humanity has not
witnessed a super eruption
•Surprise: “roots” of
magma 600 km deep towards the NW
•Extinction of
African-type animals with the eruption 12 m .y. ago. Death from
inhaling ash (glass)
Toba super eruption almost wiped out humanity 75,000 years ago
“volcanoes can kill in the distance”, causing climate change, starvation
U-shaped magma chamber monitored closely today
Week 2
Contents
•The MacKenzie Dike swarm
•The Reunion hotspot
•Paleomagnetism
Deccan Traps, India & death of dinosaurs
•Siberian Traps & Permian Death
•Video: The Day the Earth nearly Died (BBC)
•Zealandia
MacKenzie (former) hotspot
•Existed about 1,267 m.y ago
•Through NWT & Nunavut
•Created the M. Large Igneous Province which contains the largest dike swarm on Earth
•Eruption of lava 1.2 b.y. ago covered large part of NWT
Probably responsible for intrusion of kimberlites later on
•Also responsible for opening the Proterozoic Poseidon Ocean
CRB: Coppermine River Basalts – map
Mackenzie Dike Swarm – 2 maps & 3 pictures on the ground & from the air
Large dike swarms
•Have linear, radiating & arcuate distributions
•Linear maybe related to rifting & arcuate swarms may reflect regional variation in the stress field during emplacement or subsequent deformation
Another former hotspot: Matachewan dike swarms - map
Example of a later dike swarm related to the breakup of Pangea – map
Reunion hotspot: all features formed where Reunion is today
•Currently lies under the Reunion island
•The Chagos-Laccadive Ridge & the Mascarene Plateau are volcanic traces of the Reunion hotspot
•Hotspot active for ~ 66 m.y.
•A huge eruption of this hotspot 66 m.y. ago is thought to have laid down the Deccan Traps, a vast bed of volcanic lava that covers part of Central India & opened a rift which separated India from the Seychelles Plateau
•This eruption coincided with the demise of the dinosaurs, therefore eruption contributed to this extinction
•As the Indian plate moved north the hotspot continued to punch through the plate creating a string of volcanic islands & undersea plateaus (Laccadives, Maldives & Chagos are atolls resting on former volcanoes created 60 -45 m.y. ago)
•About 45 m.y. ago the mid-Indian rift crossed over the hotspot and the hotspot moved under the African plate
•Hotspot relatively quiet 45-15 m.y. ago when activity resumed and created the Mauritius, Reunion & Rodrigues islands about 10 -2 m.y. ago
•Le Piton de Fournaise, a shield volcano on Reunion is one of the most active volcanoes on Earth
Indian ocean – relief map
Mascarene plateau – map of ocean
South Mascarene islands – map of ocean
Mascarene plateau
•It extends 2000 km from Seychelles south to Reunion
•It is from -6 to -150 m below the sea. Off the plateau the sea plunges 4000m deep
•The largest underwater plateau in the Indian Ocean
•India was at one time next to Seychelles
•Seafloor spreading moved India northward
•Northern part of the plateau consist of granite, a fragment of the ancient continent of Gondwana
•The granite is topped by basalt from the Deccan Traps
•As a tropical island, Seychelles is a curiosity to have granite on it, instead of the usual coral atoll and volcanic rock
Piton de la Fournaise (top of the oven) –picture of the volcano
Part of volcano has collapsed – satellite picture
Ninety East ridge – relief map of ocean
Deccan Traps, India
•Formed 60 -68 m.y. ago at the end of the Cretaceous period, most of it erupted 66 m.y. ago. Covered half of India at the time
•Released gases particularly SO2 contributed to global cooling, prob. 2 degrees C
•The lavas are famous for the beds of fossils in between the lavas
map of India showing extent of Deccan Traps
Reason for volcanism
•Prob. associated with a mantle plume that arrived at the surface
•Seafloor spreading at the boundary between the Indian & African plates pushed India over the Reunion hotspot which now lies under this island
•The force of the Reunion plume eruptions made India move unusually fast. When the volcanic activity decreased so did the rate of plate motion
•Another reason could be the large meteor impact in Mexico, which is right across the interior of the Earth from India
•As the energy of the impact moved inside the Earth, it could have been transferred in the form of magma on the other side of the planet
•This impact was tremendous, the meteor was 10 km big
Deccan traps scenery – 2 pictures
Paleomagnetism
•Study of the record of the Earth’s magnetic field in rock. Magnetite “locks” & is a record of the direction and intensity of the magnetic field (at the time of its formation)
•Paleomagnetic evidence, both reversals & polar wandering data, was instrumental in verifying the theories of continental drift & plate tectonics in the 1960’s & 1970’s
•Magnetite becomes permanently magnetized parallel to the magnetic field of the Earth at the time of its formation
•The polarity reversal history of the Earth’s magnetic field recorded in rocks is used to determine the age of these rocks
•Reversals have occurred at irregular intervals throughout Earth’s history. The age & patterns of these reversals is known from the study of seafloor spreading and the age of the dating of volcanic rocks
How to get data
•Drill a short hole into the rock that contains magnetite, such as basalt on the ocean floor or basalt on land
•Insert a compass and angle meter to record its orientation
3 diagrams of sea floor lavas around mid-ocean ridge
Polar wander
•Tutorial at e-Education
video
•NOVA: magnetic pole flip 530,000 years overdue … (55.57)
•Magnetic field is weakening
•Protecting life from harmful space radiation
•Mars prob. lost its field & then lost its air and water (plus life) around 4 b.y. ago
•Study of pottery shows large decrease 10 % in last 300 years
•Last reversal 780,000 years ago
•On average, however, every 200,000 years
•Overdue by 530,000 years
•Detailed study of reversals shows that it weakens before it flips
•In Oregon, it lost 80% of its strength, then it changed direction slowly with daily changes
•When weak, many victims of radiation cancer
•The aurora would be visible from anywhere
•Right now South Atlantic shows evidence of a local reversal
Siberian Traps
•Movie: the day the Earth nearly died (BBC)
50 min
Igneous “provinces” – world map
Siberian traps – 1 pictures from the air & map of Russia
Video: Permian Death
•Has been a big mystery
•95 % of life died, 250 m.y ago
•New evidence in 5 steps
•1. Siberian Traps, the biggest volcanic eruption ever (flood basalts), went on for millions of years
•The big eruption of Laki, Iceland in 1783 caused a change in climate: first a volcanic winter from the tremendous amount of ash & sulfur in the air, next the CO2-rich air - after the dust cleared – caused global warming
•For extinction to occur you need a dramatic change in temperature. The Siberian Traps could raise temp. by 5 degrees C, but that won’t cause an extinction. You need an increase of at least 10 degrees C
•2. Rampino, after examining Permian rocks in the Alps decided there was a meteor impact somewhere with a body 15 km big
•3. Jones created an impact model that also created a lava flow due to the high amount of heat generated by the huge impact. Volcanism would cover over the impact crater, so you can’t find it. There should be shattered quartz crystals somewhere
•4. Antarctica has lots of Permian rocks, therefore an investigation found shattered quartz, but no iridium anomaly (seen after the Mexico impact that killed the dinosaurs)
•5. Wignell found extensive record of the extinction in Greenland. 3 distinct phases of the extinction over 80,000 years long
•First was on land, then a marine extinction coupled with an abrupt increase in C12 in the air, then a final death episode on land
•The C12 increase was due to sudden release of methane hydrate from the ocean floor
•First the lava causes global warming (+ 5 ‘ C), then warm ocean currents cause methane hydrate to be released from the ocean floor that cause a further 5 degrees C increase in temperature – a virtual Sahara desert all over the Earth!
Zealandia – relief map of ocean
Video
•Fly-over "New Zealand under the ocean" (2.00)
•A large fragment of the former supercontinent Gondwanaland. Besides the landmass of New Zealand it includes the continental shelf below water level
•For at least 400 m.y. ( up to 125 m.y ago) the Pacific plate was subducting beneath the eastern edge of Gondwana. Then rifting along the eastern edge for 100 m.y.
•Zealandia - half the size of Australia – broke off as the Tasman Sea formed
•Zealandia slowly sank as the gap widened and it stretched and thinned. Almost all fell below sea level until 23 m.y ago when a further change: plate collision & subduction along the North Island while the Southern Alps were uplifted along the Alpine Fault (recent earthquakes)
•Modern NZ has since been rising out of the sea with the much larger underwater portion still below water
videos
•"Pushing New Zealand’s boundaries"
"New Zealand: where two plates collide"
New Caledonia- picture from the air
Peridotite with nickel - picture
Green peridotite from the Earth's mantle – picture
Nickel mining (where Inco started)
•Largest ocean reserve in the world
Pine island (Ile des Pins)
•Plants survive from the age of the Dinosaurs
4 pictures from Pine Island with primitive –looking plants
The supercontinent cycle
Videos:
The Earth’s continents for past 4.4 b.years (2.05)
From Pangea to the modern continents (0.24)
650 million years in under 2 minutes
Gypsumville crater
O=limestone/dolomite, Pe= granite, J=gypsum, P=breccia, melt-rock
Notes on map
•Bump on HWY 6: where the crater rim supposed to be
•Gypsum : about 25 m thick
•Central peak: present only in large craters
•Ring (one or more): also present in large craters
•Melt-rock (like lava with gas cavities) & breccias (rocks of all types & colors mixed up) are very common in impact craters
•If there was a lot of silica in the original rock, then there would have been lots of glass beads as well – none here
Crater rim, Meteor crater, Arizona – picture
Crater
•40 km across
•13th largest on earth
•Largest in western Canada
•Impact 214 m.y. ago
•One of a chain of 5 craters: unique phenomenon
•Largest piece of meteor fell in Quebec- Manicouagan crater- more in France, N. Dakota & Ukraine
•Manicouagan at the centre (crater 100 km across), 2 craters on either side
•All craters were at 23 degrees North latitude at the time
•No Atlantic ocean then, continents were very close together (Pangea)
•Rock in Bristol, UK had a layer of glass beads: evidence of an impact with a shock wave that carried molten rock & dust – could not identify source until 20 years later
The impact 214 m.y. ago
•Killed 80 % of species
Manicouagan (“eye of Quebec”) – picture
Strange rocks to see in the crater
•Shattered dolomite near edge
•Breccias and melt rocks
•Gypsum
•Granite in centre and ring
Fractured dolomite near edge of crater – picture
Breccia – picture
Arched-up from explosion? Stone thrown up, explosion force pushed from underneath – picture
Rounded tops: rock exploded like a missile upwards – picture
Concave underneath with clay: rock pulverized where the explosion force hit the rock – picture
Expulsion cavities? CO2 gas exploded inside rock – picture
shattercones? - picture
4 pictures of shatter cones from other craters
9 m tall! : Slate island, Ont.
1 m tall: Sudbury, Ont.
Contents
•The MacKenzie Dike swarm
•The Reunion hotspot
•Paleomagnetism
Deccan Traps, India & death of dinosaurs
•Siberian Traps & Permian Death
•Video: The Day the Earth nearly Died (BBC)
•Zealandia
MacKenzie (former) hotspot
•Existed about 1,267 m.y ago
•Through NWT & Nunavut
•Created the M. Large Igneous Province which contains the largest dike swarm on Earth
•Eruption of lava 1.2 b.y. ago covered large part of NWT
Probably responsible for intrusion of kimberlites later on
•Also responsible for opening the Proterozoic Poseidon Ocean
CRB: Coppermine River Basalts – map
Mackenzie Dike Swarm – 2 maps & 3 pictures on the ground & from the air
Large dike swarms
•Have linear, radiating & arcuate distributions
•Linear maybe related to rifting & arcuate swarms may reflect regional variation in the stress field during emplacement or subsequent deformation
Another former hotspot: Matachewan dike swarms - map
Example of a later dike swarm related to the breakup of Pangea – map
Reunion hotspot: all features formed where Reunion is today
•Currently lies under the Reunion island
•The Chagos-Laccadive Ridge & the Mascarene Plateau are volcanic traces of the Reunion hotspot
•Hotspot active for ~ 66 m.y.
•A huge eruption of this hotspot 66 m.y. ago is thought to have laid down the Deccan Traps, a vast bed of volcanic lava that covers part of Central India & opened a rift which separated India from the Seychelles Plateau
•This eruption coincided with the demise of the dinosaurs, therefore eruption contributed to this extinction
•As the Indian plate moved north the hotspot continued to punch through the plate creating a string of volcanic islands & undersea plateaus (Laccadives, Maldives & Chagos are atolls resting on former volcanoes created 60 -45 m.y. ago)
•About 45 m.y. ago the mid-Indian rift crossed over the hotspot and the hotspot moved under the African plate
•Hotspot relatively quiet 45-15 m.y. ago when activity resumed and created the Mauritius, Reunion & Rodrigues islands about 10 -2 m.y. ago
•Le Piton de Fournaise, a shield volcano on Reunion is one of the most active volcanoes on Earth
Indian ocean – relief map
Mascarene plateau – map of ocean
South Mascarene islands – map of ocean
Mascarene plateau
•It extends 2000 km from Seychelles south to Reunion
•It is from -6 to -150 m below the sea. Off the plateau the sea plunges 4000m deep
•The largest underwater plateau in the Indian Ocean
•India was at one time next to Seychelles
•Seafloor spreading moved India northward
•Northern part of the plateau consist of granite, a fragment of the ancient continent of Gondwana
•The granite is topped by basalt from the Deccan Traps
•As a tropical island, Seychelles is a curiosity to have granite on it, instead of the usual coral atoll and volcanic rock
Piton de la Fournaise (top of the oven) –picture of the volcano
Part of volcano has collapsed – satellite picture
Ninety East ridge – relief map of ocean
Deccan Traps, India
•Formed 60 -68 m.y. ago at the end of the Cretaceous period, most of it erupted 66 m.y. ago. Covered half of India at the time
•Released gases particularly SO2 contributed to global cooling, prob. 2 degrees C
•The lavas are famous for the beds of fossils in between the lavas
map of India showing extent of Deccan Traps
Reason for volcanism
•Prob. associated with a mantle plume that arrived at the surface
•Seafloor spreading at the boundary between the Indian & African plates pushed India over the Reunion hotspot which now lies under this island
•The force of the Reunion plume eruptions made India move unusually fast. When the volcanic activity decreased so did the rate of plate motion
•Another reason could be the large meteor impact in Mexico, which is right across the interior of the Earth from India
•As the energy of the impact moved inside the Earth, it could have been transferred in the form of magma on the other side of the planet
•This impact was tremendous, the meteor was 10 km big
Deccan traps scenery – 2 pictures
Paleomagnetism
•Study of the record of the Earth’s magnetic field in rock. Magnetite “locks” & is a record of the direction and intensity of the magnetic field (at the time of its formation)
•Paleomagnetic evidence, both reversals & polar wandering data, was instrumental in verifying the theories of continental drift & plate tectonics in the 1960’s & 1970’s
•Magnetite becomes permanently magnetized parallel to the magnetic field of the Earth at the time of its formation
•The polarity reversal history of the Earth’s magnetic field recorded in rocks is used to determine the age of these rocks
•Reversals have occurred at irregular intervals throughout Earth’s history. The age & patterns of these reversals is known from the study of seafloor spreading and the age of the dating of volcanic rocks
How to get data
•Drill a short hole into the rock that contains magnetite, such as basalt on the ocean floor or basalt on land
•Insert a compass and angle meter to record its orientation
3 diagrams of sea floor lavas around mid-ocean ridge
Polar wander
•Tutorial at e-Education
video
•NOVA: magnetic pole flip 530,000 years overdue … (55.57)
•Magnetic field is weakening
•Protecting life from harmful space radiation
•Mars prob. lost its field & then lost its air and water (plus life) around 4 b.y. ago
•Study of pottery shows large decrease 10 % in last 300 years
•Last reversal 780,000 years ago
•On average, however, every 200,000 years
•Overdue by 530,000 years
•Detailed study of reversals shows that it weakens before it flips
•In Oregon, it lost 80% of its strength, then it changed direction slowly with daily changes
•When weak, many victims of radiation cancer
•The aurora would be visible from anywhere
•Right now South Atlantic shows evidence of a local reversal
Siberian Traps
•Movie: the day the Earth nearly died (BBC)
50 min
Igneous “provinces” – world map
Siberian traps – 1 pictures from the air & map of Russia
Video: Permian Death
•Has been a big mystery
•95 % of life died, 250 m.y ago
•New evidence in 5 steps
•1. Siberian Traps, the biggest volcanic eruption ever (flood basalts), went on for millions of years
•The big eruption of Laki, Iceland in 1783 caused a change in climate: first a volcanic winter from the tremendous amount of ash & sulfur in the air, next the CO2-rich air - after the dust cleared – caused global warming
•For extinction to occur you need a dramatic change in temperature. The Siberian Traps could raise temp. by 5 degrees C, but that won’t cause an extinction. You need an increase of at least 10 degrees C
•2. Rampino, after examining Permian rocks in the Alps decided there was a meteor impact somewhere with a body 15 km big
•3. Jones created an impact model that also created a lava flow due to the high amount of heat generated by the huge impact. Volcanism would cover over the impact crater, so you can’t find it. There should be shattered quartz crystals somewhere
•4. Antarctica has lots of Permian rocks, therefore an investigation found shattered quartz, but no iridium anomaly (seen after the Mexico impact that killed the dinosaurs)
•5. Wignell found extensive record of the extinction in Greenland. 3 distinct phases of the extinction over 80,000 years long
•First was on land, then a marine extinction coupled with an abrupt increase in C12 in the air, then a final death episode on land
•The C12 increase was due to sudden release of methane hydrate from the ocean floor
•First the lava causes global warming (+ 5 ‘ C), then warm ocean currents cause methane hydrate to be released from the ocean floor that cause a further 5 degrees C increase in temperature – a virtual Sahara desert all over the Earth!
Zealandia – relief map of ocean
Video
•Fly-over "New Zealand under the ocean" (2.00)
•A large fragment of the former supercontinent Gondwanaland. Besides the landmass of New Zealand it includes the continental shelf below water level
•For at least 400 m.y. ( up to 125 m.y ago) the Pacific plate was subducting beneath the eastern edge of Gondwana. Then rifting along the eastern edge for 100 m.y.
•Zealandia - half the size of Australia – broke off as the Tasman Sea formed
•Zealandia slowly sank as the gap widened and it stretched and thinned. Almost all fell below sea level until 23 m.y ago when a further change: plate collision & subduction along the North Island while the Southern Alps were uplifted along the Alpine Fault (recent earthquakes)
•Modern NZ has since been rising out of the sea with the much larger underwater portion still below water
videos
•"Pushing New Zealand’s boundaries"
"New Zealand: where two plates collide"
New Caledonia- picture from the air
Peridotite with nickel - picture
Green peridotite from the Earth's mantle – picture
Nickel mining (where Inco started)
•Largest ocean reserve in the world
Pine island (Ile des Pins)
•Plants survive from the age of the Dinosaurs
4 pictures from Pine Island with primitive –looking plants
The supercontinent cycle
Videos:
The Earth’s continents for past 4.4 b.years (2.05)
From Pangea to the modern continents (0.24)
650 million years in under 2 minutes
O=limestone/dolomite, Pe= granite, J=gypsum, P=breccia, melt-rock
Notes on map
•Bump on HWY 6: where the crater rim supposed to be
•Gypsum : about 25 m thick
•Central peak: present only in large craters
•Ring (one or more): also present in large craters
•Melt-rock (like lava with gas cavities) & breccias (rocks of all types & colors mixed up) are very common in impact craters
•If there was a lot of silica in the original rock, then there would have been lots of glass beads as well – none here
Crater rim, Meteor crater, Arizona – picture
Crater
•40 km across
•13th largest on earth
•Largest in western Canada
•Impact 214 m.y. ago
•One of a chain of 5 craters: unique phenomenon
•Largest piece of meteor fell in Quebec- Manicouagan crater- more in France, N. Dakota & Ukraine
•Manicouagan at the centre (crater 100 km across), 2 craters on either side
•All craters were at 23 degrees North latitude at the time
•No Atlantic ocean then, continents were very close together (Pangea)
•Rock in Bristol, UK had a layer of glass beads: evidence of an impact with a shock wave that carried molten rock & dust – could not identify source until 20 years later
The impact 214 m.y. ago
•Killed 80 % of species
Manicouagan (“eye of Quebec”) – picture
Strange rocks to see in the crater
•Shattered dolomite near edge
•Breccias and melt rocks
•Gypsum
•Granite in centre and ring
Fractured dolomite near edge of crater – picture
Breccia – picture
Arched-up from explosion? Stone thrown up, explosion force pushed from underneath – picture
Rounded tops: rock exploded like a missile upwards – picture
Concave underneath with clay: rock pulverized where the explosion force hit the rock – picture
Expulsion cavities? CO2 gas exploded inside rock – picture
shattercones? - picture
4 pictures of shatter cones from other craters
9 m tall! : Slate island, Ont.
1 m tall: Sudbury, Ont.
Week 3
Contents
•Story of geology: James Hutton (video)
•Supervolcanoes :Toba (video)
•Afar new ocean / East African Rift (video)
•Submarine volcanoes
•Kamchatka peninsula (video)
Video: The story of Geology, James Hutton
•BBC Men of Rock part 1 (59.00)
•The contribution of James Hutton, a doctor in Scotland who loved to debate
•People wondered about the Earth, how old it was
•He observed erosion while working in a farm
•Didn’t believe in literal interpretation of Bible
•His friend James Watt invented the “steam engine” (not steam power) that resembles the earth’s interior
•Volcanoes are like giant heat furnaces (where steam is generated)
•He was a genius: he could make connections between events
•An accident at a glass factory taught him a lot how molten glass (magma) cools
•His presentation to the Royal Society was rejected prob. because he was lacking in evidence – the only geology text at the time was the Bible
•His theory advanced when he found an outcrop of granite intruding sediments
•Difficult for people to believe without this evidence
•60 years later pompous Lord Kelvin rejected Hutton’s theories, but he contributed by estimating age of the earth from time to cool a molten globe (20-40 m.y.). No one believed him either
•Hutton’s unconformity at Siccar Point however, became a world monument
•The discovery of radioactivity in 1898 proved that Hutton’s theory was correct
•The age of rock comes from crystals of zircon after measuring the uranium / lead ratio inside this mineral
•The age of Scotland oldest rocks came to be 2.6 – 3.0 b.y.
Unconformity at Siccar Point, Scotland
Supervolcanoes
•The story of Toba
Video: Mystery of the megavolcano
•Research for 15 years started with samples of ash at the bottom of the ocean: from a volcano but which one?
•Independent research by two others on other topics
•1st clue: Greenland in 1988 Zielinski studied composition of the atmosphere. He found an unusual abrupt anomaly 75,000 years ago with a sulfate content 40 times the normal
•Must have been a thick blanket of sulfuric acid droplets in the air
•2nd clue: Rampino studied oxygen atoms in shells of sea-bottom forams to measure temperature. He came across an abrupt anomaly of a 5 degrees C drop in temp. some 75,000 years ago. That was a catastrophic event like an ice age
•3rd clue: Other researchers were studying the depth of water in Lake Toba. It was very deep, like a big hole and all around the lake were thick deposits of igneous rock from magma. Ash samples matched ash found at sea bottom in the ocean and both were 75,000 years old
•There is subduction under Lake Toba, some 30 km below surface
•Huge reservoir of magma
•“Supervolcano”: at least 1,000 km3 of ejecta
•A 2 km deep hole after explosion was filled by rainwater
•NASA simulation of eruption. Sulfuric acid cloud can turn planet into Ice Age; plants die, animals & humans starve (60 % of humans died), forams die in the ocean
Supervolcano
•Term not used in scientific work until recently
•Due to large amount of lava and gases it can cause dramatic change in the weather & extinctions
•It can be two types: large igneous provinces & massive eruptions
•Can form at a hotspot (Yellowstone) or at subduction areas (Toba)
Afar: new ocean is born
•A triple junction of plates (also a hotspot)
•Part of East African Rift
•Rifting started 25 m.y. ago (Red Sea 30 m.y.)
•Behaves like a mid-ocean rift, but started as continental flood basalts in several places (Ethiopia, Somalia & Kenya). Continued as rifting with magmatism along the entire rift system
•Reactivation of old faults and development of new normal faults typical of all rifts
•Not all volcanoes are equally active
•Many volcanoes were created by the rift, but not all of them lie along the rift today
•The Lengai volcano is the only natrocarbonatite volcano in the world. It has no silica, crystallizes in midair and shatters like glass!
•The rift system is the largest seismically rift on Earth today. Strongest quake was 7
•A significant source of early human fossils
•The rapidly eroding highlands quickly filled valleys with sediments, thus easy to preserve remains
Erta Ale, Ethiopia
•A continuously active basalt (like ocean) shield volcano
•Surrounding area below sea level
•Has the longest-existing lava lake
•Volcano over the East African Rift system
•Not studied much as terrain most inhospitable –very hot, salty desert, even Afar people are vicious to strangers
Video: Erta Ale, Ethiopia
•Part of the East African Rift
•Sulfuric acid pools – the acid cooks food like a microwave oven
•Pools may also contain extremophiles which can be used to fight diseases
•The pH of the pools is below zero! Extreme!
•That means magma is just below
Active rifting
•Fissure opened up a few years ago
•Soil temp. up to 97 degrees C
•Gases escape, esp. deadly H2S
Lava lake
•One of 4 in the world
•This is the oldest
•Volcano has 2 craters
Submarine volcanoes
•The most productive volcanic systems on Earth are hidden under an average 2.6 km of water
•Mid-ocean ridges produce an estimated 75% of the annual output of magma
•The magma & lava create the edges of new oceanic plates and supply heat & chemicals to some of Earth’s ecosystems
•They produce life & metals
•There are over a million submarine volcanoes
•Perhaps 75,000 of these rise over 1km above the ocean floor
Kamchatka, Russia
Almost like a volcanic island
•Is a World Heritage Site
•Has endemic plants and other unique animals/plants
•11 species of salmon co-exist
•Surrounded by water that does not freeze & has relatively mild climate
•One of the most volatile (volcanically) regions on Earth
•Video: Smoking beauties, Kamchatka (25.50)
•29 active volcanoes (300 total)
•You can take an arduous trip to see them
•Volcanic glass, sharp rocks, steep slopes, up to 3 km high
•Very explosive volcanoes (rich in silica), gases could not escape through lava
•Volcanic bombs, dust, mudpots
•Rocks rich in sulfur, copper, iron
•900 degrees C in fractures, put your stick in & will catch fire instantly
•Terrain was test ground for lunar vehicles
•Climbers have to keep constant pace for easier breathing
•“Valley of geysers”, 2nd biggest after Yellowstone
•City of Petropavlovsk has 2 volcanoes behind it
several pictures of volcanoes, geysers, mud pools of Kamchatka peninsula
Uzon caldera
Several pictures with CO2 gas bubbles, geysers & hot pools
week 4
Presentations
•Pompeii & Herculanium
•Deccan Traps, India
•Iceland: volcanoes
Hecla, Katla & Eyjafjallajokull
•Yellowstone supervolcano:
there have been 3 previous eruptions of this volcano
Popigai crater, Siberia
•4th
largest crater on Earth
•100 km across
•Remote north of
Siberia, restricted access: reason? Full of diamonds
•There is graphite in
the original rock, the pressure of the impact turned them into diamonds!
•Formed 35 m.y. ago,
probably twin with Chesapeake crater in the USA
•Probably the biggest
collection of diamonds in the world, if it goes in production, all other
diamond mines will close
•Hint: look for diamonds
in other craters if graphite is part of the rock (in Gypsumville no hope!)
Video: Supercomet,
After the Impact
•Discovery channel
•by Jay Melosh, Univ of
Arizona
•Stations: Hawaii,
Paris, N.Y., Mexico, Cameroon
•Arecibo dish, Puerto
Rico: biggest “eye” to the sky
•Impact at Yucatan,
Mexico
•EM pulse destroys all
electronic equipment by release of electrons
•Auroras everywhere
•Dark Age
•Fallout: ash, burning
rain, tsunami
•Some people refuse to
move
•Heat wave reaches the
Pacific, 100 degrees C, a storm of fire
•All forests burn,
acid rain, temp. reaches 300 degrees C
•One can only survive
underground
•Sunlight gone,
eternal night
•Plants sprout, but
they get exhausted and die
•Fungi rule the earth,
they don’t need light
•Darkness causes Ice
Age
•The frozen frogs of
Canada: They hibernate
Field Trip to the Gypsumville Meteorite Crater
shatter cone (?) from the Gypsumville meteorite crater
Classes at the Fieldstone office, Ashern
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