Geog Final

What instrument does Pat use to measure amount of elements in a sample?

Mass Spectrometer

Why yse lead in Roman Plumbing

Its cheap and easy to work with

Why is lead toxic to humans?

Gets into cells and does not allow enzymes to do their job

What was the additive used in leaded gasoline?

Tetraethyl lead, its fat soluble

Who was Robert Keyhoe?

Scientific expert for the lead industry

How do we know that lead levels in nature were typical but not natural?

Using old glacier ice cores, deep vs shallow ocean

Planet

• Is in orbit around the sun

• Has sufficient mass to assume hydrostatic equilibrium (nearly round shape)

• Has “cleared the neighbourhood” around its orbit (pulled debris toward the center of earth

Four Terrestrial Planets

Mercury, Venus, Earth, Mars. Inner planets

Jovian Planest

Jupiter, Saturn, Uranus, Neptune, Outer planets

Dwarf Planets

Ceres, Pluto, 2003 UB313

Asteroid Belt

Separates the terrestrial and jovian planets

How do we know what earth looks like?

The sound waves from earthquakes

Earth’s Layers

1. Outer Crust

2. Partially molten upper mantle

3. Solid lower mantle

4. Liquid outer core

5. Solid inner core

Uniformitarianism

• The idea that things in the past lead to today

• Hutton, Lyell, Darwin

• Earth is old, gradual processes take time to form earth

Catastrophism

• The idea that Earth was created through supernatural means and affected by a series of catastrophic events

• Earth is young, formed by catastrophy

• Cuvier

Acasta Gneiss

Oldest dated rock on earth, 3.96 billion years old. Found in Northwest Terretories, Canada

Earth’s Age

• 4.6 Billion Years old

• Encompasses the planets formation and origin of life/evolution of biosphere

Manageable Time

Earth has long periods of time when nothing happens

Eons

Hundreds of millions to billions of years

Eras

Many millions of years: distinctive fossil records

Periods

Millions of years: distinctive rock units

Epochs

Few Million Years

Ages

Thousands of years

Endogenic Processes

• Internal system

• Flows of heat and material from below Earth’s crust powered by radioactive Decay of unstable elements

• e.g. mountain building, earthquakes, volcanoes

• Potassium-40, Uranium-238, Uranium-235 and thorium-232

• At 80-100 km deep temp is 650-1200 C

Exogenic Processes

• External system

• The motion of air, water, and ice powered by Solar Energy

• e.g. all processes of landmass denudation such as physical and chemical weathering, landslides

Denudation

Process of layering

Migration of Heat through Earth

• Endogenic

• Heat energy migrates outward from center by conduction

• Heat energy migrates outward from the more fluid/plastic layers in the mantle and near the surface by convection

Deepest Mine of the Earth

Roughly 4km

Deepest drill holes of the earth

12km

Earth’s Crust

• Outermost, rigid layer- relatively thin

• Thickness caries

  • Oceans: 8-10 km

  • Continents: 40 km

Continental Crust

• Generally lower density

• 2.7 g cm³

• Granite, Igneous rock

Oceanic Crust

• Higher Density

• 3.0 g cm^-3

• Basalt, extrusive igneous rock

Mantle

• Mostly Solid

• 2900 km thick

• Temp and Pressure increase towards centre

• energy transfer towards surface increases

• Asthenosphere and Lithosphere

Asthenosphere

Partial Melting zone in the mantle

Lithosphere

Rigid layer in the mantle

Core

• Interior is layerd

• Inner Core

  • solid iron, high pressure won’t let rocks melt.

  • Temp is 2500^oC

• Outer Core

  • Molten Iron, lighter density, high T’s cause rocks to melt

Earth's Magnetism

• Magnetic Fiel and magnetosphere generated by fluid outer core

• Thermal and graviational energy to magnetic energy

• North magnetic pole moves

Average Period of Geomagnetic Reversal

• 500,000 yrs, varies

• Tool for dating rock units and understanding plate tectonics and movement

Endogenic System (geological cycle)

Building Landforms, building up

Exogenic System (geological cycle)

Eroding landforms, breaking down

Geological Cycle

• Endogenic and Exogenic systems

• Heat from solar energy and internal heat

• Tied to hydrological cycle, rock cycle and tectonic cycle

Eight Major elements of rock cycle

O, Si, Al, Fe, Ca, Na, K, Mg

Minerals

Natural components with specific chemical formula, crystal structure

Rocks

Group of minerals or solid organic matter

Sedimentary Rocks

• Sedimentation and lithification

• Stratigraphy

Igneous Rocks

• 90% of rocks

• Small and large grained rocks: cooling rate

• Intrusive and extrusive rocks: batholiks, dykes vs volcanoues

• Felsic of Mafic: elemental contents

• Includes all of the mantle and oceanic crust, most of the continental crust

Granite

• Intrusive igneous rocks

• Cools slowly below ground

  • Large crystals

• Felsic, lighter colour, less dense

Basalt

• Extrusive igneous

• Cools rapidly on the surface

  • very small crystals

• Mafic

Mafic Rocks

Darker and denser

Felsic Rocks

Lighter colour, less dense

Metamorphic Rocks

• Changes by temp and pressure

• Regional vs. contact metamorphism

• Folated or not: mineral alignment

• Gneiss, Marble, Slate

Alfred Wegener

• Developed the theory of continental drift, but not a mechanism as earthquakes were not yet understood

• Argued that the Earth’s continents were once joined together as one (Pangea) and moved apart over millions of years

Polar Position: 440 MA

• Yes polar position

• Yes ice sheets

Polar Position: 390 MA

• Polar position: Yes

• Ice sheets: No

Polar Position: 300 Ma

• Polar positon: Yes

• Ice Sheets: Yes

Polar Position: 260 MA

• Polar positon: Yes

• Ice Sheets: Yes

Convection Cells

• Fluid movement

• Hot mantle material rises, moves outwards, cools, and leads to eventual collision and subduction

Gravity push/pull

When lava rises, the weight of thickening plate goes down

Plate motion per year

1-12 cm, depending on the direction and location

Wilson Cycle

• A model that explains how continents repeatedly come together and break apart over billions of years

• The mass of continents trap geothermal heat in Earth, like a blanket which eventually weakens the crust

• Four steps: Assembly, stability, splitting, reassembly (500 mil years)

• Terrane accretion and exotic terranes are physical evidence

Orogenic Episode

Mountain building events caused by collisions

Terrane accretion

chunks of crust added to continents

Exotic Terranes

Crustal fragments that originated far away

Divergent Boundaries

• Plates pulling away from eachother, leads to splitting continents

• New crust forms as magma rises, creates mid-ocean ridges and rift valleys

• e.g. Mid-atlantic ridge and east African Rift

Convergent Boundaries

• Two plates move toward each other, when hthey colllide, they compress and one crust sinks beneath the other

• Create mountains, trenches, earthquakes, and volcanoes

Convergent Ocean Plates

• One oceanic plate subjucts beneath the other to create trenches and volcanic isalnd arcs in the subduction zone

Convergent continental plates

• Neither plate is dense enough to subduct, so they crumple and thicken.

• Forms:

  • Huge mountain ranges (e.g., the Himalayas)

  • Strong but shallow earthquakes

  • Very little volcanism

Convergent oceanic and continental plates

• The denser oceanic crust sinks beneath the lighter continental crust

• Creates volcanic chains on land (e.g., the Andes), Deep ocean trenches, Powerful earthquakes, Magma formation as the subducting plate melts

Transform Faults

• Two techtonic plates sliding past eachother horizontally

• Little to no volcanism, earthquakes are common, no crust created or destroyed

Tension Stress

• Rocks are pulled apart which stretches and thinks the crust

• Produces normal faults

Compression Stress

• Rocks are pushed together which shortens and thickens the crust

• Convergent boundaries

• Produces reverse faults

Shear Stress

• Rocks slide past each other and bend horizontally (like two books past eachother on a table)

• Produces strike-slip fault

• Common at transform boundaries

Folding

• Caused by compression at convergent plates

• Create wave-like structures

• Anticlines and synclines

Anticlines

• Arch shaped folds, the oldest rock is in the center

Syncline

Trough-shaped fold, youngest rocks are in the center

Basin

Layers warped upward in a circular pattern

Basin

Layers warped downward in a circular pattern

Faulting

• Fracture of material and displacement

Normal Fault

• Caused by tension (pulling rocks apart)

• Hanging wall moves down from the footwall

• Common at divergent boundaries

Thrust Fault

• Caused by compressional stress (pushing rocks together)

• Hanging wall moves up from the footwall

• Common at convergent boundaries

Strike-slip Fault

• Caused by shear stress (horizontal movement)

• Rocks slide horizontally past each other

• Common at transform boundaries

• Create offset ridges

Orogenesis

• Mountain building from rocks under stress

  • folding/faulting

  • plate collision

  • terranes (small crustal fragments)

  • volcanoes add material

  • uplift

• e.g. rocky mountains (ocean to continent), appalachians, himilayas (continent to continent)

Earthquakes

• Series of shocks caused by movement of crust or upper mantle, often along fault lines

• Stress pass the threshold point which leads to sudden failure

• Deepest foci and greatest stresses produce most intense earthquakes

Focus

The point of failure for earthquakes

Epicentre

The point on the earths surface above the focus

Seismographs

Record earthquakes

Richter Scale

• For earthquakes

• Each step represents 10x increase in energy

Aftershocks

Occur due to continued slipapge along the same fault after main quake

Denudation

The lowering of continental surfaces accomplished through weathering, mass wasting and erosion

Physical Weathering

• Breaking down rock into smaller pieces, does not change chemical composition

• The numerous smaller pieces are more easily eroded

• Frost action, salt weathering, pressure-release jointing, biological forces

Chemical Weathering

• Chemical composition is altered (decomposistion)

• Reactions between air, water and minerals in rocks

• Occurs faster in wamer temps with abundant water (e.g. tropics)

• Disrupts crystal structures of minerals in rocks, so they’re more succeptible to physical weathering (they accelerate each other)

• Hydrolysis and Hydration, Dissolution of carbonates

Mass wasting

Transfer of material downhill via gravity

Erosion

Transfer of material by water, wind and ice (weather related phenomenon)

Frost Action

• Repeated cycles of freezing and thawing to break rock into smaller fragments

• Water expands 9% upon freezing

• Physical Weathering

Salt crystal growth

• Water evaporates, leaving salt in the rocks which physically breaks them up over time

• Mostly in dry environments or in areas with ocean spray

Pressure-release jointing

• Expansion of rock from removal/erosion of overlying rock— reduction in pressure

• Creates slab-like layers/sheets break loose

Biological Activity

Physical weathering of rock from activities of plants and organisms (e.g. clams)

Hydrolysis

• Free H or OH ions of water do chemical reactions to produce different compounds

• Feldspar+Carbonic Acid and water—> residual clays + dissolved minerals + silica

• Crystal structure of weaker minerals can breakdown and lead to granular disintegration

Dissolution of Carbonates

• Reactions where carbon combines with minerals and dissolves them

• Weak carbonic acid reacts w/ many minerals containing Ca, K, Mg, Na

• e.g. weathering of limestone exacerbated by acid rain

Karst Topography

• Solution of carbonate rocks (i.e limestone) can result in a landscape of pitted, bumpy surface topography w/ underground channels and caverns

• Rocks mus be high w/ > 80% CaCO3 and have jointing (natural cracks)

• Must be enough precipitation to supply the water with warm enough temps to keep reactions going

• more vegetation=more CO2=more karst

• e.g. Tower karst of Guanxi Province, Southern China