EESA06 Lecture 1
Planet Earth 2011
– Earth is 4.5billion years old
– Geography of planet has changed, Plate Tectonic Movements
– Rocks can tell us the history of the planet – where water was, where land ones
– Glacial erratic – large boulders
o Marble – altered limestone
– Super-continent – Pangaea Great – all together in one place
– Amnesia Continent – Pangaea # 2 – will become a super continent once again
– Stratigraphy – putting rocks in their relative age – organizing history
o Aka Historical geology
– Vector Map – direction of movement and velocity of movement of land masses
– Next super continent clustered around southeast china
– Ring of Fire – most dangerous place to live, the outline of pacific
– Geophysical Equipment – cameras etc. go underwater
– Derrick – drilling tower
o The Resolution – drill ship can drill 7km underwater
Scope of Course
– Earth history: Application of ‘plate tectonics’ to the ancient past to reconstructing past
continents/oceans
– Paleo-environment reconstruction (ex: climate) and paleo-biology
o Paleo = old
– Geographical evolution of Canada over 4 billion years
– Environmental issues and hazards (earthquakes etc) resources (mineral, water, oil)
Lecture 1 and 2:
How Planet Earth Works: Plate Tectonics (Chapters 1 and 2 in textbook) Key concepts to read up for the First Two Quizzes:
– Formation of planet Earth 4,500 million years before present ‘Continental drift’ and Pangaea: 1912 (Alfred Wegner)
o He proposed that craters on the moon were caused by meteor impact – Sea Floor Spreading: 1960 (Harold Hess)
o Oceans are widening, pushing the continents around
– Magnetic stripes on the ocean floor and wander paths for continents: 1965 (Fred Vine)
– Mid-ocean ridges and hot spots: 1965 (Tuzo Wilson)
– Plate Tectonics and Wilson Cycle: 1967 (Tuzo Wilson)
o Continental drift (continents are moving around) vs. Plate tectonics (whole of earth surface can be broken up into plates and those plates are moving due to mantel movement)
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Change in the Earth’s Interior – Differentiation – caused by gravity [diagram]
Differentiated into a core, mantel and crust
Degassing – Minerals break down in volcanoes, created water vapor, accumulated on earth’s surface as oceans
Plumes – the uneven core, composed of plastic rock that is hotter than surrounding mantel, want to rise Brittle crust – being moved around by plumes in mantle
Old crust – sinking back into the mantel
Mantel Convection – continuous stirring of mantel – hot rock (plumes) coming up, cold hard rock going
down
Heat source – is from radioactive decay of uranium
– However, over time earth is cooling
Diamonds come from the layer immediately around the core – about 2billion years old
The United Plates of Planet Earth
– Biggest plate – Pacific Plate
– Mid-ocean ridge – row of volcanoes running thru the middle of the Atlantic ocean
John Tuzo Wilson is the father of Plate Tectonics
Type of Crusts:
– Oceanic crust 5-8km thick 7km/sec – higher density sink lower into mantel
o Made up of basalt rock
– Continental Crust <70km thick 6km/sec – low density
o Dominantly made out of Granite
- Mohorovicic (Moho) – the base of the crust
- Asthenosphere – low velocity zone, very weak, plastic
Geothermal energy – heat coming from the mantel
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EESA06 Lecture 2
The deepest mine in the world is 4km underground, any deeper it will be too hot, hole will begin to close due to temperature and movement
Geophysics – application of physics to the world
Earthquakes – generate energy
- Fault plane – surface (between moving bocks) which blocks have moved, we feel as an
earthquake
- Focus – is where the energy is released, the trigger of the earthquake, always underground, can
predict how much damage it can do – how deep down the focus is
- Epicenter – directly above the focus on the earth’s surface
- Seismic risk assessment – gauge any movement along any fault, looks at fault scarp & fault trace
- Fault scarp – cliff, bluff, the steep slope that results after earthquake (ex: 1891 Japan)
- Fault trace – fairly straight lines, many river valleys along traces of faults
o Morphological – what shapes on earth’s surface created by faults
- Not all faults create earthquakes, some “creep” don’t result in earthquake, the “lock” ones
create earthquakes Waves:
- Body waves – goes thru the interior
o Primary and Secondary waves
- Surface waves – go around the surface
- Primary waves – the quickest 7km/sec, compression + extension (spring)
o can go thru fluids
o go all the way thru the interior of planet, thru the core
o Refraction effects create “shadow zones” – no direct P waves
- Secondary waves - are smaller 5km/sec, wave on a rope o Cannot go thru fluids
o stops at core
o very large shadow zone Earth Core:
- Outer most part of core is liquid – preventing s-waves, refracting p-waves
- Inner core is solid
Seismograph station – closer to focus = time lag of arrival of P&S waves not much, farther from focus = time lag from P&S wave is bigger
- Allow to determine where the epicenter was
- Networks was setup to determine nuclear bomb testing
Major Epicenters – Circum-Pacific belt (most damaging, deepest), Indonesian belt, Mediterranean- Himalayan belt (where India is colliding with China)
- Deep focus earthquakes - Along the plate margins
- Deepest earthquake is 7km down
- Shallow-focus earthquakes, where plates are diverging, mid ocean drifts
- Low magnitude earthquakes, magma coming up
- Earthquakes can be in the middle of continents
- Intracratonic earthquakes – are very difficult to explain and predict (ex: Toronto)
Ancient China used missing farm animals to predict earthquakes
Using Heat Flow measurements to map mantle structure and plumes (very hot rock)
- Black lines are continents – cooler areas
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- White lines are the plate boundaries – higher heat flow below the oceans
Picture of the Core by Julain Lowman
- Large plumes protruding from the core
- Green slabs going down into core
- Plates are moving around due to convection in this interior
Rift valley on ridge crest (in textbook!) – seems like a conveyer belt
- Hot mantle rising and cold mantle sinking
- Oceanic trench - Oceanic crust meeting oceanic crust (Older oceanic crust more dense goes
under less dense, younger oceanic crust, continental crust goes on top, least dense)
- Island arc – considered continental crust
- Andesitic volcano
- Mid-oceanic ridge Rift valley
Finger nails grow at average of 3.7cm/year, Atlantic ocean opening growing at 3.7cm/year
Crust types: two (continental and oceanic) and so plate interact in four ways: 1) divergent plate boundaries (mid ocean ridges, continental rifts)
2) oceanic crust converging with oceanic or continental (“subduction”)
3) continental crust converging with continental (“obduction”)
4) Both types of sliding past each other (“transform” boundaries)
Continental Drift: (Alfred Wegener)
- 1912 published theory of continental drift
- Proposed a supercontinent Pangea – fitting the continents together
Pangea consists of:
- Laurasia (N.America & Asia)
- Gondwana (Southern continents)
- Wegner suggested continents moved by plowing thru sea floor but this mechanism was rejected
by most scientists...
- Put a map together, by identifying rocks of the same age, evidence that the plates were once together
Striation - Scratches in rocks made by glaciers (thick mass of ice that is flowing, usually has rock debris)
- Tell us about the direction of ice flow in the last ice age about 10thousand years ago
Ocean floor gets mapped
- Sound source - mimics energy that is produced by earthquakes – generate seismic signals
- Hydrophone – picks up the bounced off energy from the ocean floor, reconstruct ocean floor
- Swath Bathymetry – higher frequency waves, bounce off the surface of ocean floor
- Can map subduction zones, mid-ocean ridges
The Challenger Deep aka Marianna trench – deepest point of Pacific ocean, 11km deep, just above a subduction zone
Topography of the ocean floor
- Fractures – transformed faults, horizontal lines – offsets mid-ocean ridges
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Harold Hess (1962) – introduced the idea of the sea floor spreading
- Sea floor created at Mid-Ocean Ridges (MOR)’s recycled into mantle at trenches
Paleomagnetism
- Periodically the Earth’s magnetic field flips
- North magnetic pole changes to south
- Geographical pole and magnetic pole do not coincide
Direction of Earth’s magnetic field
- Cooling lava <- Magnetic alignment preserved in magnetic records orientation of Earth’s fields
- Geomagnetic Time scale - Layers of rocks – lava flows showing reverse magnetism
Paleomagnetism
- Magnetic reversals in lavas average every 500k years
- Takes 10k years or less for a reversal to occur
- Magnetic epochs: Brunhas -> Matuyama -> Gausis -> Gilbert
Magnetic Stripes
– Magnetometer – tow behind ship, measure magnetism on ocean floor (cannot see)
– Magnetometer survey of ocean floors identified patterns of anomalies on each side of MOR’s
– Symmetric pattern on either side of the ridge
– Patterns Matched pattern of magnetic reversals
– Proved the sea floor spread
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EESA06 Lecture 3
How continents Break Up and Oceans Open
– Mantle movement creates – Triple junctions – 3 major fractures
o Middle of continent, dome forms above plume, o Outward flow from plume creates rifts
o Only one rift develops into an ocean
– Failed rifts are preserved in modern continents from the breakup of Pangea – they just sit there and may fill up with sediments
– Example of failed rifts in Canada: Ottawa river valley and St. Lawrence river valley
o Control river flow, generate earthquakes
Stage 1: East African Rift
– Continent undergoes extension, the crust is thinned and a rift valley forms
Stage 2: Red Sea
– Continent tears in two, continent edges are fractured and uplifted, Basalt eruptions form
oceanic crust Stage 3: Atlantic Ocean
– Continental sediments blackout the subsiding “pressure” margins to keep continental shelves, the ocean widens and a mid-ocean ridge develops as in the Atlantic Ocean
Difference between a Sea and an Ocean
– Ocean has a mid-ocean ridge, and always widening
– Seas do not widen
East African Rift System
– Continental breakup and birth of a new ocean
– Somalian plate – the “horn” of Africa will break away and become an ocean
– Triple Junction – Gulf of Aden, Red Sea, Lake Turhana (one of these will become an ocean)
Arabian Plate
– Pushed north by the widening of the red sea
Fissures – cracks in the earth’s crust
– Basaltic magma comes out thru the fissures, generates flood basalts
Ash layers – can put an age on it
Early hominids started in East African Rifts – Kariandusi (layer of ash founder hammers)
– Homohabilis – tool maker hominids
Where is an ocean opening today?
– When there are lots of oceans there is lots of food – rich ecosystem, key step of human
evolution took place when there were large oceans
Afar Triangle – Rift widening, famous for human evolution (Lucy – australopicthin)
– Thinned crust, Flood Basalts
– Danakil Desert
– Shield Volcano – low slope tips, source of flood basalts, basalt eruptions (building oceanic crust)
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– Pointy Volcanoes – have more violent eruptions , gas doesn’t come out as readily, magma is more stiff
Deccan Lavas – cause extinctions
Margin of the Red Sea – Egypt
– Nile river – flowing from East African Rift, Ethiopia, Parallels Red Sea
– Giza (old period – pyramids made out of limestone) and Luxor (new period – temples made out
of granite) – population clustered around these two places Pyramids: all constructed approx 4,500 years ago
1) Great Pyramid of Khufu (Cheops) – Tura limestone facing stone
2) Khafre’s Pyramid (Chephren)
3) Menkaure’s Pyramid
“the idle and foolish exhibition of royal wealth”
“soliders, forty centuries of history look down upon you”
Bioclastic Limestone – made up of broken fossils (foraminifera – nummulites organisms)
– Numismatics – study of coins, they look like coins hence the name
Mokkatam Limestone – Thin bedded “world’s first stone building” stripped of its Tura limestone Tura limestone – polished, mirror like
Electrum – the gold caps on pyramids
Pylon – at Karnak temple complex: made out of Nubian sandstone
Hypostyle hall in Luxor: made out of Nubian sandstone
Tors – granite (igneous rock) rots along fractures when it is in a warm climate
– Regolith – clay material, rotten granite
Canada does not have Tors because of glaciers, knocked them down and moved boulders all around
– Erratic boulders – glacial transported boulders, remains of tors
Obelisk – tall towers of limestone
Gold is an igneous rock – was thought to be the skin of the gods, Nubians bringing tributes of gold
The oldest known Geological Map: 3150 years old
– Written on papyrus for Ramesses IV by Ammenakhate (“Scribe of the Tombs”) and portrays
Wadi (Canyon) Hammamat in the Eastern Desert
– Where gold veins were etc.
William “Strata” Smith – the map that changed the world
– Smith was a canal engineer and made the first geology map in Britain in 1815
– Industrial revolution – the need to find coal etc
William Logan – the First Canadian Geology Map 1866
– No coal problem – Nova Scotia Confederation to get coal from others
Daily reminders of an ancient past
Rock names having an ancient Egyptian source:
1) Porphyry – igneous rock with very large crystals, deep red almost purple color (mined in egypt and exported by Romans for coffins)
2) Basalt
3) Alabaster
4) Syenite – type of granite, common in southern Egypt
5) Ophiolite
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Red Sea is opening up – Mountains are result of Arabian plate crashing into European plate:
– Arabian Plate is Pushed North Along the Dead Sea Fault Zone as the red Sea Opens
– Turkish Plate is “escaping” Westward along the North Anatolian Fault
– North Anatolian Fault – major fault and major earthquakes
– Dead Sea Fault Zone – Arabian plate sliding past crust to the west, major earthquakes
Dead Sea – a lot of evaporation produces brine
– Brine – concentrated salty water, At least 10x denser than normal sea water, unable to swim
– Lowest Place on Earth – subsiding rift, well below sea level
– Level of Dead Sea is lower – commercial use of salt
Lisan formation sediments – looking for evidence of ancient earthquakes, major earthquakes disturb layers of rock formations, earthquakes falls in cycles, may give clue to next earthquake
– Seismites – layers of sediment of rock that have been deformed by major earthquakes
– Comparing written records of earthquakes (“the dead sea scrolls”) and information from
seismites to find frequency of earthquakes
Crusader Fortress of Ateret on the Jordan River: Built on a Plate Boundary
– Earthquakes of 1202 and 1759 moved 2.1m North
Wall offset by slip along plate boundary
– Sinai-Israeli Plate on left and Arabian Plate on right
Petra, Jordan – city built into rocks (was in Transformers) – Abandoned due to an earthquake
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EESA06 Lecture 4
Topics for Lecture 4 and for Quiz 3 on Thrusday Feb 10th
1) Introduction to mid-ocean ridges: Modern and Ancient “Fossil” MORs (Called Ophiolites)
2) Why are more MORs Fractured? The role of transform faults
3) Iceland: Walking over a Mid-Ocean Ridge
4) Magnetic Stripes Recorded in Ocean Floor Crust and The Age of Ocean Floors
5) Basalt Lava Flows: Fissure Eruptions
6) Volcanic Activity Under Glaciers: Jokulhlaups!
7) Geothermal Energy
Oceans only widen(rift) to a certain width then they start to close – subduction
– cooling away from ridge and thickens at sides
– It wants to sink back down to the mantle
– History of continent is dictated by ocean history
Ophiolites – Ancient pieces of ocean crust
– Combining the information can put a picture of
history of MORs
– Contain rocks that are very mineral-rich
Mid Ocean Ridge
– Middle of Atlantic, constantly volcanic eruptions
– Are not continuous, are fractured
Fractures – horizontal lines on MORs
– enable ocean floor spreading on a curved earth
surface
Dykes – result of hot magma intruding into older rock, sheeted Dykes – surrounding rock will be extended
– basic fuel behind plate tectonics Plumes – supply the large amounts of magma How Oceans Widen: Continuous intrusion of dykes
– continuous cooling of margins of magma chamber and continuous intrusion of new magma at center
– symmetrical distribution on each side
Pillow Basalt – pillowed lava, rounded masses where basalt magma was cooled very quickly Gabbro – chemically equivalent of basalt but has larger crystals since it cools slowly, igneous rock Peridotite – dominant mineral is olivine (Peridot), the mantle is made out of peridotite
Distill – Gabbro and Basalt is distilled from huge
mantle plumes
Ridge Push- Hot magma pushes up and dykes intrude Slab pull – Ocean floor sinks under its own weight Continental crust – is the product of melting ocean crust plus sea water
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Ma – Mega-annum (million)
Ga – Giga-annum (billion)
ka – kilo-annum (thousands of years) 750Ma to 350Ma
– closing of an ocean – aiapotis
– oceanic crust – some gets subducted, some gets
pushed up onto land (Himalayas)
– Ophiolites – ancient ocean crust that is now on
land, fossil ocean crust preserved on land Eastern Canada:
Chert (Flint) – sediments that were being slowly deposited on top of MORs, igneous processes, and accumulates
Sheeted Dykes – continuous intrusion of basalt
Pillow Lava – igneous rock, cooled very quickly
Oceanic crust is made of:
– Mafic and Ultra-Mafic rock– magnetism and iron,
pre-dominant in olivine Contiential crust is made of:
– Acidic Rocks – more silica Red – is young Green + Blue is old Youngest Rocks are all along the MOR
Pacific ocean can see old rock but not along south American coast
– Oceanic crust has already been subducted
– Feeding Andian Volcano, has been recycled
Maximum age of oceanic crust is:
– Late Jurassic (150 mill. years ago) – Pangea broke up
Continent underlay by two plumes, push two contintents apart,
flood basalts develop into oceans
fractures allow spreading on curved surface or when there is weakness in the crust
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Fractures – a crack or break
– Black arrows moving in the same direction
Transform Faults – movement of rock on either side of a fracture (can be small or big – San Andres Fault)
– Black arrows moving opposite each other
Hydrothermal Processes – Super heated water
– Vents carrying minerals in suspension, looks
cloudy and opaque
– Ancient ocean crust is a major source of metals
Iceland is an example of a hotspot
– Hotspot = a narrow plume (the red dots)
– Hotspots are stable (40 in the world)
Volcano is above the hotspot
– Crusts are moving, volcano dies but a new one
forms
– End up with a chain of volcanoes
– Older volcanoes are smaller due to erosion
Distillation – Melting of Plumes – withdrawing fluid from what was plastic
Iceland is slowly being torn into two
– Sitting on a MOR
– West on north American plate
– East on European plate
Rate at which plates are moving in Ontario = 3cm/year
Fissure Swarms – group of cracks (2 pictures)
– These cracks wells up magma
– Krafla Central Volcano – overdue for a major
eruption, huge amounts of ash in air Symmetrical: very young island ->
– lots of small earthquakes
Transform Faults Zone (TFZ) – Iceland region
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Magnetic Stripes
– – – –
Thingvillir – –
Switches through time
Ocean crust is being pushed away, acquire magnetic strip along the edge Confirms sea floor spreading
Dangerous to walk over magnetic stripes
plate boundary for north America
First Iceland parliament held there – natural amphitheatre
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Measuring the Jerky movement of plates using a GPS Ultra-Mafia Rock – Shield Volcano
Acidic Rock – Pyroclastic Cone
Eruptions – shape volcanoes and what rock is formed
Mid-Ocean Ridge
– Mining heat in the circle in the form of hot water
– Geothermal energy
Spatter cone:
– Cinders – large pieces of rock, rapid cooling of lava that
is hot up into the sky
Ropey Lava – A cooled lava flow
– Very fluid magma looks like when its cooled
– Pahoehoe lava
Sharp/ Jagged (cooler) -Aa lava
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Quiet Volcanism
– Basaltic lava flows easily
– (low viscosity) – water moves easily
– Two types of lava
o Pahoehoe – ropey (hot lava)
o Aa – cinders, sharp, jagged (cooler)
Oil thick = high viscosity, use in high temperatures Oil thinner = low viscosity, use in low temperatures
Flow = used to be a lava flow, ropey surface – Dykes feeding to magma surface
Basaltic Flow that has cooled inside – Paligonal rocks
– Contracted and then broken
– In Iceland are said to be “trolls”
Tephra – Volcanic Dust, can affect climate Glacier sitting on a dormant volcano
Tuya – Flat-top mountain, erupted underneath ice made of basaltic
– Sub-glacial volcanic eruptions – under ice
Pillow lava – from erupting in water
Jokulhlaups (Joo-kulh (mountain) laups (leap))
– Big Floods coming out below ice-caps (Similar to flash floods)
Geysir – water goes down gets heated above boiling point, under pressure, form spray of water – Happens every 10-15 mins
Boiling mud pits…
The Blue Lagoon – hot water, contains algae (fine rock particles), distinctive blue color
Icelandic Deep Drilling Project
– Geothermal Energy – draw hot water for energy – Can grow bananas – wells in yard
– Earthquake proof pipes
Reykjavik – “Smokey Bay” – capital of Iceland
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– District Heating Project – steam, free hot water
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EESA06 Lecture 5
When oceans close is the dangerous volcanoes – because of subduction.
Raeology – ability to flow, how easy does that magma flow?
– Iceland is very fluid – not that dangerous, all gases come out
– More viscosious – dangerous, stuff comes out – pyroclastic
– Pyroclastic – broken by fire, rocks are shattered by eruptions and thrown up into air
– Volcanic bombs or ash(is a misnomer – named improperly)
o Italy thought it was coal burning
The Green Areas – subduction back into the mantle
– Friction (earthquakes), melting (volcanoes)
– Similar to lava lamp
The Pacific Ring of Fire: Tectonics of a closing ocean
– Pacific Rim – Dense concentration of volcanes, major
earthquakes, tsunamis
Subduction:
– The stars marks earthquakes – The deepest earthquakes are
700km down
– We know that slabs don’t melt till after 700km down
– Magmatic Arc – a line of volcanoes directly above
subduction zone
– Oceanic crust – made out of basalt
– Silicic magma – Sediment + seawater melted, reducing
viscosiy of magma
– Deep water trenches – ocean floor going down into
subduction zone
New Zealand: small island, exposed tip of a much larger land mass (Zealandia)
– Red Boundary – Pacific plate and Austrailian Plate
o Bottom: Austrailian Plate is being subducted under
Pacific Plate
o Top: Pacific Plate is being subducted under
Austrailian Plate (older oceanic crust is heavier) o Middle: Obduction – Colliding continental crust
together
– Obduction – Himalayas, creating high mountains
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Continential Crust Collides with Continenetial Crust:
– The Southern Alps – Mt.Cook in New Zealand
White Island – young volcano
– Lateral (side) blast – highly dangerous
– Caused by sector colapse
– Sulfuric acid – natural pollution
Merapi Volcano – Indonesia’s most dangerous
– Killed the gate keeper that protected the volcano
Subduction: Older oceanic crust going under younger crust
– Japan & Indonesia
– When you collide two oceanic crust,
creates continential crust, generates new
lands
– Proto-continents – first continents
Model of Merapi – Steep Volcano – very susceptible to sector collapse
Eruption:
1) Pyroclastic Flow – White areas – with gas and boulders
2) Lahars – debris flow – similar to concrete
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Merapi’s sister – stable
Top of Merapi – very unstable because has thick plug of magma being pushed up, building a cap and its beginning to fall off – Large cracks
When erupts – gase and large masses of rock rolling down – Pyroclastic flows
– Rich soils – farming at base of volcano
After the pyroclastic flows – the large boulders – Mt.Winson killed 30 journalists
Flow deposits – burnt stuff buried – Charred woods – dark oval
Japan: Volcanic arc
– Earthquake nation, most danergous place on pacfic rim
– More volcanoes, active faults
– Tokyo – four plates combined here
Arc of volcanoes becomes an island
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Chikyu – the earth
– Drill ship – can drill 7km down into ocean floor
– Made out of derrick – the drilling apparation
– Riser system – can withstand high gas pressures
– Want to drill down into mantle – new source of energy +
mineral deposits etc.
– Want to find an early warning system for earthquakes
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Mount Fuji and the City of Fujioshida
– Famous for fire festival
– Make offerings to the volcano
– Pyres – light these for celebration
Mount Unzen of Japan’s Deadliest Volcanic Disater in 1792
– Green patches from sector collapse
– Under pyroclastic flow is the older city
– fishing ports
– Islands as a result of sector collapse
– Sector collapse triggers a tsunami – “double whammy”
The Legend of the giant kashima (cat fish)
– Geo-methology – how they used to explain earthquakes
Nobi Earthquake of 1891
– 1868 – western technology in japan
– 1891 – All the western building fell down
Neodani Fault
– Earthquake museum
– Fell 6metres
Tokyo after the great Kanto Earthquake of September 1st 1923
– Kill people by fires + buildings coming down
– Survivors of 1944 earthquake
– Earthquake prevention day – Sept 1st
San Francisco
– San Andreas fault – transform fault
– From Plates sliding past each other
– Connects sea floor spreading in south
and trench forming in the north
– Baja is on its way north to Vancover
Western Canada (Yukon, Alaska, California)
– Made up of pieces of crust come up from
south and got stuck at Western America
– Making way up from San Andreas Fault Creeping Segment (Blue) – fault is continuously
moving , release of stress
1906 break (red) – locked fault 1857 break (green) – locked fault
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San Francisco – Bay Area
– Hayward Fault-along shoreline, where San Andreas splits into 2
Building that survived the 1906 earthquake – Because built on rock not sediment
Effect of Liquefaction: Subsidence of Houses
– Anything solid when shaken turns into liquid
– Houses sunk down, second floor became main floor
University of California in Berkley
– Hayward Fault – runs right in the middle of centerfield
Standford is built on the San Andreas Fault
– when shaken the left statue fell, memorial arch damaged
Hollister – Creeping Plates
– San Andreas Fault Creeping Fault Line:
– Not dangerous
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Cobija: Devastated by a Tsunami in 1877
– In a James Bond Movie
– Used to be part of Boliva but now its part of Chile
Concepcion Earthquake of 1835 Witnessed by Charles Darwin
– Land was raised up several metres
– Darwin – Made connection how earthquakes and how
mountains are pushed up
– Andes Mountains have been jacked up by earthquakes
Salt Flats – Salars in Atacama Deserts
– Driest Desert on the planet
– Contain Lithium – used for batteries
Nitrate Mining in the Atacama Desert
– Fixation of nitrogen from the air by bacteria
– Nitrate Deposits – for fertilizers, expolsives
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Chile: Strato-Volcanos – the dangerous ones
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Lascar Volcano: Chile’s most Active
– Farmland over pyroclastic flow
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Lava Flow coming down the valley
Chaiten
Chaiten Volcano
– Pyroclastic Material coming up
– Very stiff magma
– Caldera – hole left from previous eruption
– Growing of volcanoes
– Old Volcanic Glass – Rhyolite – Obsidian, used for
arrowheads, knives
– Can fingerprint Rhyolite – trade between ancient people
Plume of ash: coming away from Chaiten Volcano What it looks like today
Forests blown away but pyroclastic flow
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Small city of Chaiten
– Gases wiped out vegetation
Town of Chaiten Devastated by a Lahar in 2008 – Lahar – River of mud
1) Subduction Oceanic and Oceanic
– Older goes below younger
2) Subduction Oceanic and Continential
– oceanic goes under continential
3) Obduction: Continential and Continential – pushes land up into mountains
4) Sliding: no subduction or obduction
– San Fran: Locked
– Hollister: Creeping
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EESA06 Lecture 6
Fossils
– Step 1: The earliest Bacteria: 3.8 Ga(?)
– Step 2: The Cambrian Explosion: 542 Ma (multicellular animals with shells, backbones etc)
– Step 3: Diversification During the Paleozoic: c.400-250 Ma
– Step 4: Role of Meteorites
– Nova DVD: Becoming Human
Evolution of Earth:
– Hadean Period – “hell on earth” – Rocks was molten, no water no atmosphere
– Diversification – heavier elements sank to the middle
– Magnetic field – to hold on to the gases – which build up atmosphere + oceans
How are fossils formed?
– Shells buried and preserved unaltered (<100 million years)
- Mineralization - Cavities are filled with silica, calcium carbonate, iron (ex: tree stumps)
- Most fossils are found in sedimentary rock
o Exception: Pompeii people covered by pyroclastic flow and fossilized in ash Per-mineralization
- Die in or near water
- Soft parts consumed by bacteria
- Sedimentation (fine grained =more detail, chemical makeup of rock = color)
- More sediments pile on = pressure – rock
- Mineral rich water = changes to the shell
- Uplift – by continental crusts coming together (plate tectonics)
- Erosion – wear away rocks
Ammo – an organic gemstone
Ammo fossils – iridescent aragonite with trace elements
(Fe, Mn, Al, Ba)
Trace Fossils
- Preserved tracks, trails, burrows (protection/food), borings
- Ichnology – study of trace fossils
- Bioturbation – process of disturbing sediment
Fossils as clues to ancient environments
- Palaeocology – study of ancient organisms and their environments
o (St.Cuthbert rings, Sea Lily - Crinoide)
o Clues from: fossil types, assemblages (group of
fossils tend to be found together), fossil
morphology, trace fossils Fossils and stratigraphy
- How do we use fossils in stratigraphy?
o to establish relative age of rock units, correlate units
- What information do we need to do this? o Relative age of rock units
o Fossil species present in each unit
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lite
nite
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EESA06 Lecture 6 Page 2 o Geologic range - Establish time of first and last appearance of each species
William Smith – Principal of Faunal Succession – fossils appear in layers
What kinds of Fossils are most useful for stratigraphic work?
- Index Fossils (ex: Ammonites) - Are Short-lived and widespread
- Assemblages (groups) of species
Trilobite Growth
- Trilobites molted regularly – shed skin
- Thus very abundant in the fossil record
The evolution of Life on Earth...
- Intense bombardment from 4.5 to 4 Ga prevented life becoming established
- No magnetic field to prevent oceans and atmosphere being stripped off the planet’s surface by
the solar wind?
Sir James Dawson – was wrong.
- Thought to be the oldest fossil Eozoon Canadense (1868) – ‘the dawn of animal of Canada’ now recognized as mineral not organic – dubiofossil
Step 1: The Earliest bacteria 3.3 Ga (?)
- Prokaryotes – some are photosynthetic (called cyanobacteria: blue/green algae)
o Microscopic, single-celled, lacking a nucleus
- The earliest prokaryotes (the Archaea) lives around superheated waters near submarine
volcanic vents (hyperthermophilic)
o Simple bag-like cells
o Only life forms between 3.8 and about 2 Ga
Where on Earth did early life forms flourish?
- Probably in oceans – salts, solvents, mixing of elements to create organic compounds
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- Life forms may have first developed at hydrothermal vents (mid-ocean ridges) At Modern Hydrothermal vents (called smokers) on mid-ocean ridges:
- Microbes – hydrothermophiles
- Live at temps > 100C
– No light
– Energy from chemosynthesis – ex: sulfur
Gunflint Formation (in Ontario) – prokaryotes
– 1.9 billion – once thought to be the world’s oldest fossils
Oldest Cyanobacteria are thought to be 3.5 billion years old from the Apex Chert in Western Australia
– They may be dubio-fossils… entirely of mineral origin, not organic
Stromatolites (Gk for ‘stoney carpet’)
– most common Proterozoic fossils made up of colonies of prokaryotic bacteria trapping fine sediment on sticky bacterial mats
– Modern relatives still survive in hyper-saline lagoons in western Australia
The “Rusting” of the Earth c. 2.8 Ga
– Hydrothermal Delivery of Dissolved Ferrous Iron at Mid- Ocean Ridges
– Cyanobacteria – created oxygen as waste
– Oxygen – oxidized ferrous iron
– Ferric iron oxide droplets – landed on bottom
– Turbidity Current
– Deposition of iron oxides as banded iron formation (BIFs)
o No longer made Cyanobacteria created the World’s Iron Ore
– Banded iron ore – alternating layers of magnetite (greyish black) and hematite (red – iron rich mineral ) + red jasper (quartz)
– Largest deposits are in Canada (Labrador) shipped to steel plants in great lakes (ex: Hamilton)
The Rise of the Eukaryote Bacteria
– First developed at c. 2.8 Ga as single cells (protists) with thick protective walls (their fossil
remains are called achritarchs)
– They reproduced sexually which allows genetic mutations to be inherited from one generation
to another
– Mobile and actively sought food using their hairs (cilia)
– The first multi-celled eukaryotic organism (called metazoans) were the Ediacara that developed
about 630million years ago, these are the earliest true animals (resemble jellyfish and worms) Mistaken Point NFLD
– Mistaken Point formation, NFLD has one of the earliest multi-cellular animals known
– Between 635 and 543 million years old
– Soft bodied – very hard to fossilize, buried quickly
– May have been like a jellyfish
– One of the Ediacaran biota
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Step 2: The Cambrian Explosion 542 Ma (Multi-cellar animals) The breakup of Rodinia between 750 and c.600 Ma
– New habitats – shallow waters near continents
– Sudden appearance of principal animal groups between
600 to 542 Ma
– Shelled forms capable of burrowing into sediment for
food and shelter
– (bad news for geologists: why?) – Bioturbation
Cambrian North America – period of “tectonic stability”
– Atlantic coast in modern day – Maritimes east coast have a passive margin
– Modern day west coast is active margin due to subduction
– Divergent passive margins carbonates, sands deposited in shallow inlands seas
o Clastic things – sands, clays, silts, carbonates (coral reefs) etc.
o Many habitats for animals to develop Cambrian Explosion
Metazoans – Multi-cellular creatures appeared ~630 million years ago – Ediacaran fauna (ex: Kimberella, Sprigginia)
o Complex forms – discoidal, frond-like, elongate
o Soft-bodied
– May be related to accumulation of free oxygen in atmosphere
Mistaken Point Formation: Newfoundland
– A united nations biosphere reserve
– Earliest multi-cellular life forms at 575 Ma (faun like)
The Burgess Shale
– Discovered by Charles Walcott near Field British Columbia
in August 1909
– In 3 field seasons he collected over 60,000 specimens
– Now a UNESCO World Heritage Site
Strange Creature of Burgess Shale
– Hallucigenia (40cm)
– Anomalocaris (60cm)
– Pikaia earliest chordate (4cm) – creature with a backbone
– Opabinia (7cm)
Step 3: Diversification During the Paleozoic c.400-250 Ma Palcozoic = Old Life
– Families of marine organisms increased from 160 to 530
o Diversity among trilobites, brachiopods, bivalve mollusks, gastropods (snail-like)
– What caused this increase in diversity?
o Mountain building, volcanism – starting to build Pangea o Increased habitat diversity?
Typical Reef Community “Limestone Builders”
– Coral reefs the hard parts builds limestone
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Step 4: Mesozoic – middle life period
– around Cret-Tert time – Major extinction of dinosaurs (around 65 million years ago)
o Due to a meteorite hitting earth near mexico?
– Around Pr-Tr time – Major major extinction – 90% of marine families went extinct during
o Due to flood basalts?
– After extinction of dinosaurs, mammals became dominant
Human Evolution and the Onset of Ice Ages
NOVA: Becoming Human – Unearthing Our Earliest Ancestors
– Nothing is more fascinating to us than, well, us. NOVA’s groundbreaking investigation explores
how new discoveries are transforming views of our earliest ancestors. Featuring interviews with renowned scientists, footage shot as fossils were unearthed, and stunning computer-generated animation, Becoming Human brings early hominids to life, examining how they lived and how we became the creative and adaptable modern humans of today
http://www.pbs.org/wgbh/nova/evolution/becominghuman-part-1.html
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