ESS 103: Sept 9 20130909
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Canada Rocks: The Geologic Journey – Nick Eyls and Andrew Miall (Read?)
Covering: geologic hazards, how we interact with earth, pollution, natural resources
Current federal government very antienvironmentalist as compared to previous liberals, especially forestry
and fishery protection.
FIRST TEST: OCT. 16 Av: 60% NOV 25 TH
TUTORIALS: Help Center instead of tutorials.
What is the earth?
Earth System Science (4) Solid earth (lithosphere) – hydrosphere (water); biosphere (animals) and resting on top is the atmosphere
Four spheres that govern Earth Processes
Open and closed systems
Closed system: earth functions as a closed system most of the time. Sun is only thing that goes into our
Open system: Exception i.e. asteroid, cloud of earth system shields atmosphere to create a nuclear winter
3 Major Components (5)
crust (750 km) (two types; upper and lithosphere – see diagram on slide 6), mantle (plastic, high temp.,
moves as a slow liquid) (2900 km) and core (iron nickel; responsible for magnetic field) (2250 km).
oceanic crust: consists of basaltic rocks ; more dense
continental crust: granitic rocks
How do we know about the earths interior?
Seismic information (P and S waves)
Slide 8 diagram
Primary: arrive first; push pull waves; “childs toy”;
Secondary: shake waves; “shakey rope motion”; energy comes back; moves somewhat slower than P
S waves do not pass through liquids
Seismographs: detecting the motion of the crust Locating an earthquake: P waves travel faster than S waves. The spacing between the P and S waves
indicated the distances the waves have travelled.
(Earthquake located at the intersection of circles) diagram
Wave paths and Swave shadow
S waves not transmitted through liquids and this is one of the main ways we know the earhts core is liquid.
S waves do not travel across the opposite ends of the earth.
Xenoliths: fragments of host rock brought to the surface by igneous intrusion.
Meteorites: 2 basic types
Assumed that meteorites represent the breakup of a planet much like our own
DIFF between mineral and rock:
MINERAL: Any naturally occurring solid that is crystalline and has a specific chemical composition
ROCK: any naturally occurring aggregate of minerals.
The Rock Cycle
Escape of heat from the mantle through convection
Ie overturn of water in a boiling pot
Generally runs over oceans, creates new igneous material
THREE TYPES OF ROCK:
Igneous: rock cooled from molten state Ex basalt (oceanic crust), granite (continental crust)
Sedimentary: rock formed from recycling of materials at the Earth’s surface
Sandstone; dolomite of rocky mountains, containing fossil reefs
Metamorphic: Any rock altered by heat/pressure
Earlier rocks that have been recrystallized, ie highway in cottage country
SEE CHART ON SLIDE 17 TO EXPLAIN CYCLE
Iron (most prominent in the core), oxygen, silicon and aluminum are the most common elements
Carbon notably not on this list
composition of crust and interior are diff (ie whole earth most iron, crust in most oxygen) Plate Tectonics 20130909
theory that explains the global distribution of geological phenomena such as seismicity,
volcanism, continental drift, and mountain building in terms of the formation, destruction,
movement, and interaction of the earth's lithospheric plates.
Arabian continent moving north relative to Africa, opening up the Red Sea (newer ocean), creating a major
fault zone along the course of the Jordan river and the Dead sea (dead sea rift).
Old testament describes walls falling, etc. but can be attributed to earth quakes caused by the dead sea rift.
Plate tectonics evolved from ideas about continental drift
Pangea: sediments/fossils lead to current understanding of shape
Animals evolve based in isolation as continents separate
The Interior Heat Engine
Tectonics driven by earths ‘heat engine’, heat generated by dispersed radiogenic elements
Convective overturn of mantle = boiling pot of water
Takes millions of years
Continental plates forming crust rafted on mantle, carried away from sea floor spreading centres,
and periodically collide, creating mountain belts.
The Overturn of Earth’s crust
Hot mantle rock rises
Cold sea floor and mantle rock sinks Plate Tectonics 20130909
New crust emerges, causes earthquakes
Movement of oceanic crust away from spreading centres rates at 3.7cm/ year = average growth rate of a
Proof of sea floor spreading
Proved by examination of the Hawaiian islands
volcanic islands get older as you track them westward,
Major processes of plate tectonics
New crust is created by injection of magma at sea floor spreading centres
Oceanic crust is recycled by descending into the mantle at SUBDUCTION ZONES. Partial melting of
material generates new rock
Continents split and separate
Rifts form first, as in east African rift system
I.e. Vancouver islands
Faults are pushed up causing big earthquakes
SEPT 16 TH
Popocatapetl Volcanoes in Mexico City (july 2013) Plate Tectonics 20130909
Converging Continents cont
Severe earthquakes occur where plates overlap in the subduction zone
Coastline keeps being pushed back by northward driving force of Indian driving plate
Rockies: process of compression pushes up thrust vaults
Grenville continent: comparative to india Asian orogeny
Now muskoka, high mountains all eroded away (similar to Himilayas) ie roadside highway is erosion of
Third type of plate movement
Where plates slide past each other
Ie san andreas fault los angeles/ san fran area.
Earth Major Plates
Heat leaving earths interior causes movement
Suduction zones cause great earthquakes, volcanoes
Age of Earth’s Oceanic Crust
Majority of crust is newer, oldest being 160 million years. Plate Tectonics 20130909
Compared to earths age being 4 billion
Due to contstant recycling process: rock cycle, sear floor spreading, subduction, etc.
Magnetic field not testable material.
Movement of Plates
Based off of gps lat and long comparative.
Every case, there is motion. Earth always moving.
Bleak subduction off of phillipines and japan
East pacific rise is moving towards south America vs plates in Andean mountains are in same direction but
move at different rates, creating subduction zone.
Lateral movement in all directions dependent on active zone,
Present type: ethiopa can currently see new oceanic crust being formed
Types of Faults
One block will rise over another at the fault plane
Reverse (left up)
Normal (right up)
Strikeslip (left moves southernly, right moves northerly)
Oblique slip (left moves upwards and southernly) Earth Systems and Cycles 20130909
Earths Energy Budget Earth Systems and Cycles 20130909
From sun (measured in watts)
Ie lightbulb 40100 watts
Sun 17.3 x 10 ^ 16 watts (billion years before it red giants)
Energy that drives photosynthesis/other biochemical proceses
Sun energy creates land sea earth,
some reflected back into space as heat and light energy
Absorbed by greenhouse gases in the atmosphere
Some heat created by convection (11.3 x 10^12 watts)
Oceans occupy over half of earths space = blue planet
Reflects back suns energy
Absorbed by atmosphere (64%)
Much energy absorbed by land and water
Heat transfer by air and water
Hemisphere will alwayds be hotter than poles
Surplus equater heart drives currents that carry the heat
Due to earths rotation, causes a moving object to be deflected to the right in the northern hemisphere:
Heat transfer occurs in hurricanes Earth Systems and Cycles 20130909
Earth’s Climatic Belts
Most of world greats deserts are located between tropic of cancer, equator and tropic of Capricorn.
Heat of the sun causes air to rise and create moist air currents, water condenses and becomes rain =
characteristic of equatorial zones.
Air descends and causes high pressure zones, ie central atlantic, Africa, etc.
Dropped moisture over equator
Air Circulation and Wind Patterns
Hadley cell shows the rise of moist tropical air, mixes with other air masses – ferrel cell dry air, and polar
cell. See chart
All weather comes from the west
Trade winds, (get def), belts of deserts, equatorials rain forests are all located in accordance with these
World surface ocean currents
Currents driven by wind pressures and energy transfers
I.e. gulf stream – climate following stream varies, stream just moderates
Satellite sensor image shows diff in water temp.
Water naturally forms border seas and whirlpools
Sinks around Greenland sea Earth Systems and Cycles 20130909
Great Ocean Conveyor System
Complete continuous circulation of ocean waters
Takes about 1000 years for complete cycle
Large masses of cold water sink to the bottom of the atlantic ocean = cold current flowing in a southernly
Goes to southern atlantic
Artic flows easternly – isolated by worlds weather system – this is why its always cold
The Water Cycle
Clouds formed by evaporation for ocean lake water, picked up by surface air masses and condensed into
Moved by weather and fall back into rain
Some will fall onto elevated surfaces and turn into snow or ice – some will become glaciers
Water on elevated areas flows off and returns into seas
Vegetation serves to cool and moisten a climate
Deforestation turns an area arid
I.e. Africa around 0 AD were fertile soil until over farming deteriorates soil and climate change –> dry
Inventory of water at Earth’s surface
Groundwater compared to oceans is low
Residence time of water found in reservoirs
Slow movement of ground water = why some areas lack water supply. Earth Systems and Cycles 20130909
Industrialization and burning of fossil fuels increases CO2 in atmosphere
Organic matter becomes transported into ocean through respiration and decomposition – sediments in
ocean (sedimentary rocks) > coal, oil and gas OR ocean CO2 store which is diffused into atmosphere
Long process – we are consuming far faster than created
Est. stores of carbon
Atmospheric co2 is relatively low to oceanic co2, very low compared to marine sediments and sedimentary
MOST CARBON IN NATURE IS PRESENT IN LIMESTONE
Long term: return of carbon to atmosphere is not a huge problem to the earth,
Geologic Time Scale *
CN Tower demo: Time has “speeded up” – very tip is recent cenozoic life. (humans)
a. Origin of planet earth: 4.5 billions of years. (ga)
b. ArcheanProterozoic boundary: 2.5 GA
c. Beg of Phanerozoic – 600 millions of years (ma)
d. End of the cretaceous – 65 ma
e. Humans – 5 ma
Recorded history – 4 – 5 thousands of years (ka) Earthquakes 20130909
Build up of stress and release along a pre existing fault plane – movement sends shockwave
• Earthquakes indicate that rock deformation has occurred
• This causes bending (folds) and fracturing (faults)
• This deformation occurs because rocks are under stress
• Earthquakes occur when buildup of stress leads to sudden release of energy
• Stress is caused by the lateral movement of the Earth’s plates
• Two types of stress: Extensional and contractional stress
• Rocks have a certain elasticity that permits ductile deformation and the formation of folds.
• Beyond a certain point they will fracture, forming faults
• After a quake there is Elastic rebound or “snapback”
• Types of fault: normal, reversed, thrust, strikeslip
Primary (push waves) and secondary (shake waves)
Major plates are continental and oceanic , all occur at or near plate boundaries
Circum pacific belt (edge of North America)
Great number of earthquakes also occur in southern Asian
Most occur in unpopulated oceanside areas with little damage Earthquakes 20130909
Scale indicates strength, rank from under 2 being small, upwards of 8 is massive destruction
Logarithmic scale – each magnitude is 10 x more powerful than the next lower magnitude on the scale.
Greatest loss of life occur in 3 world countries – high population and poor building standards
Worst in recent years: Haiti – poor contributes to high casualties
Port au Prince located on major fault
High amount of earthquakes – rarely hear about vast majority!
Fires, landslides, liquefaction of clays, changes in ground level (flooding by the sea or
drying out of harbours), tsunamis,
Older foundations , ie built on sand/clay, in an earthquake had motions can liquefy foundation, causing
buildings to collapse
means down going of oceanic plate at the edge of a continent
deepest points in ocean occur near subduction zones
ex) Sumatra boxing day 04: tsunami from indian ocean
ex) Japan fragile location, high pop
Fukushima – hit coastline nuclear power stations 20130909 20130909
Weeks 4: Volcanoes 20130909
Slide 2: Volcanoes are the most visible product of the process of melting in the Earth’s interior.
This map shows the location of the world’s major volcanoes. They occur in three main settings:
1) Along subduction zones
pacific ocean = ring of fire (where most of the words active volcanoes are)
2) At midoceanic spreading centres ie Iceland
3) Above mantle plumes: rises directly upwards, sheds molten lava from top of plume into
ocean floor (e.g., Hawaiian volcanoes)
Slide 3: terminology:
Magma: molten igneous rock Hea ing of the mantle generates molten magma (see platetectonics
section: Week 02A).
Lava: molten igneous rock extruded and flowing on the earth’s surface
Intrusive rock: a body of magma that has pushed its way into host rocks
and cooled below the Earth’s surface
Extrusive rock: a body of lava poured out and cooled at the surface 20130909
Pluton: A body of igneous rock cooled at great depth (several km),
usually consisting of coarselycrystalline rocks, such as granite
Pyroclastic rocks: From the Greek work pyro for fire and the word clast
meaning broken. Fragmented volcanic rocks formed at the surface
Ash or tephra: blobs and drops of lava cooled quickly in air and fallen to
form a blanket on the surface
The main features of a subduction zone. : magmatic arc
*TRY TO FIND VIDEO EXPLAINING THIS?
Illustrates examples of the plutonic rocks (granite) that form the roots of most subduction zones.
Minor types of igneous intrusion (see inset in Slide 4 for explanation of terms)
Slide 7: **
Main types of volcano 20130909
oceanic sourced volcanoes (shield volcano)
—basalt, 50% silica, Forms oceanic crust. Rocks are rich in the minerals of iron and magnesium, which
gives the rocks a very dark, commonly almost black colour.; non explosive; free flowing lava
crustal source (stratovolcano)
—andesite lava and tephra, mixed lava and ash, light grey
—rhyolite and andesite lava, 70% silica, high viscosity (flows slowly like toffee) and very explosive > forms
granite intrusions. Formed by partial melting of continental crust in subduction zones. Rocks are pale in
colour bc of silica, often pink or red.
Shield volcanoes in Hawaii
Characteristic “ropy” lava texture of fresh lava (this view is of a flow only a few weeks old). The texture is
formed when the surface crust cools and rumples up like a table cloth as the molten lava below continues to
Slides 14, 15:
When a lava flow enters the sea if forms characteristic “pillow lava” texture. This pair of slides shows a
modern and an ancient pillow lava field.
Slides 16, 17:
Modern lava flows. The heat sets all surface vegetation and human constructions alight. This is the “fire” of
the Ring of Fire, a secondary effect of volcanic eruptions. Lava flows, including lava fountains, are not “on
fire”. They are red because they are hot, not because burning is taking place.
Spatter cone (top) and blacksand beach (bottom). Local erosion of fresh lava flows in Hawaii creates
beaches composed of lava fragments, and fragments of the minerals of which the lava composed. In places
the main beach material is black basalt fragments, as shown here. In other
places beaches are composed of the green mineral olivine.
Slide 19: The effects of the eruption in Iceland in April 2010: unusual amounts of ash shut down
transAtlantic air travel for weeks. Volcanoes 20130909
Lecture 04B Volcanoes 20130909
These are the main types of volcano that form in magmatic a