EAS 2600 Unit One (Lectures 1-9)

Transform Boundary:

• Motion

• Crust

• Earthquakes

• Mountains

• Volcanism

• Motion: Plates slide past each other

• Crust: Not created or destroyed

• Earthquakes: Shallow

• Mountains: None

• Volcanism: None

Example: San Andrea’s Fault

Divergent Boundary:

• Motion

• Crust

• Earthquakes

• Mountains

• Volcanism

• Motion: Plates move apart

• Crust: Creates youngest crust on planet

  • Mantle is brought to the surface by decompression melting

• Earthquakes: Shallow

• Mountains: yes

• Volcanism: yes

Example: Mid Atlantic Ridge

Convergent Collision Boundary:

• Motion

• Crust

• Earthquakes

• Mountains

• Volcanism

• Motion: plates move towards each other

• Crust: not created or destroyed

• Earthquakes: shallow - moderate

• Mountains: yes, produces highest mountains

• Volcanism: no

Example: Himalaya Mountains

Convergent Subduction Boundary:

• Motion

• Crust

• Earthquakes

• Mountains

• Volcanism

• Motion: plates move towards each other

• Crust: destroyed, produces deep oceanic trenches

• Earthquakes: shallow to deep

• Mountains: yes

• Volcanism: yes

Example: Andes Mountains

Earth’s physical layers

lithosphere, asthenosphere, mesosphere, outer core, inner core

Earth’s chemical layers

crust, mantle, core

inner core state of matter

behaves like solid

inner core composition

iron and nickel

outer core state of matter

liquid

outer core composition

iron and nickel

asthenosphere is part of the ___

upper mantle

asthenosphere behaves like _____

plastic

lithosphere is what ____

breaks into tectonic plates

lithosphere is the _____

cool and rigid rocky outer layer of the Earth

lithosphere thickness

varies. Smaller in oceanic regions (50-100 km). Thicker in continental regions (130-160km)

crust physical composition

lithosphere

mantle physical composition

lithosphere, aesthenosphere, mesosphere

core physical composition

outer core, inner core

Who proposed continental drift theory in 1912?

Alfred Wegner

Wegner and Continental Drift Evidence

Matching coastlines, similar geographic features and rocks, location of glacial evidence and coal deposits, fossil locations,

biggest criticism of continental drift at the time

Wegner did not provide a mechanism for how the continents were moving

who created the first detailed maps of the ocean floors?

Marie Tharp

Vine-Matthews-Morley Hypothesis (1963)

Ocean floor was created at the mid ocean ridges and pushed away (provided evidence for idea of seafloor spreading that was proposed by Hess)

Earthquakes

The sudden release of strain energy in the Earth’s crust, resulting in waves of shaking that radiate outwards the earthquake source

If you take an overall average of the crust, mantle, and core, the two most abundant elements are?

iron and oxygen

Yellowstone and Hawaii represent a _____

hot spot

crust is created at a ____ boundary

divergent

What are some main features than can emerge because of the subduction motion at convergent boundaries between an oceanic and continental plate?

deep earthquakes, ocean trenches, volcanoes, mountains, shallow earthquakes

what type of tectonic boundary would you experience shallow earthquakes, mountains, and volcanoes at?

divergent

The Appalachian Mountains currently represent a/an ____zone and the Andes currently represent a/an _____zone. 

passive; active

why does oceanic crust subduct underneath continental crust?

it is more dense

T/F: Because of the current plate tectonic motion, in millions of years the Atlantic Ocean will be larger than the Pacific Ocean

true

dominant chemical element in the mantle

oxygen

layer of Earth responsible for generating Earth’s magnetic field

outer core

chemical composition of Earth’s core

iron and nickel

plate tectonics is the theory that the lithosphere is _____

broken into plates that move relative to each other

T/F: The lithosphere includes both the crust and the uppermost rigid mantle

true

T/F: S-waves can travel through both solid and liquid layers of the Earth

false

oceanic crust is generally (older/younger) than contiental crust

younger

Which of the following are mechanisms that drive plate motion?

• ridge push

• slab pull

• mantle convection

• Earth’s magnetic field

• ridge push

• slab pull

• mantle convection

max depth (in km) of deep-focus Earthquakes

700 km

which layer behaves plastically over geological time and allows tectonic plates to move?

asthenosphere

describe oceanic crust

thin, basaltic, and relatively young

Which scientist proposed mantle convection as a possible mechanism for continental movement?

Arthur Holmes

Which tectonic boundary type produces the highest mountains on Earth?

convergent collision

where are igneous rocks common?

igneous rocks are very common at divergent, convergent subduction, and hotspots

extrusive igneous rocks

when lava solidifies on the surface

intrusive igneous rocks

when magma solidifies underground

extrusive igneous rock example

basalt

intrusive igneous rock example

granite

how are igneous rocks classified?

they are classified based on rocks texture (whether they are intrusive or extrusive) and composition

extrusive textures

glassy, vesicular, porphyritic, fine grained (can’t see many crystals)

intrusive textures

course grained (can see crystals)

texture of igneous rocks is primarily controlled by _____

cooling rate

most abundant mineral group

the silicates

mineral classes

1. silicates

2. sulfides

3. oxides

4. halides

5. carbonates

6. native metals

7. sulfates

Silicate Structures

Isolated Tetrahedra, Single Chain, Double Chain, Sheet, Framework

Isolated Tetrahedra Structure

no oxygen atoms shared, tetrahedra bonds by cations

Isolated Tetrahedra Structure EXAMPLE

olivine

Singe Chain Structure

Each tetrahedron shares two oxygen atoms

Single Chain Structure EXAMPLE

pyroxene

Double Chain Structure

Tetrahedra shares two or three oxygen atoms

Double Chain Structure EXAMPLE

amphibole

Sheet Structure

2D. Tetrahedra share three oxygen atoms

Sheet Structure EXAMPLE

mica

Framework Structure

3D. All oxygen atoms shared

Framework Structure EXAMPLE

quartz and feldspar

Bowen’s Reaction Series

Describes the temperature at which minerals crystallize when cooled, or melt when heated

specific gravity describes a mineral’s ______

relative density

what is mineral cleavage?

the tendency to break along planes with weaker atomic bonds

difference between a reserve and an ore

reserves are already identified deposits; ores are useful metallic minerals that can be mined at a profit

critical mineral

a non-fuel material with a high supply-chain risk and an essential function in one or more energy technologies

what does a larger difference between P-wave and S-wave arrival times indicate?

a greater distance from the earthquake

what does Bowen’s Reaction Series describe?

the temperatures at which minerals crystallize when cooled or melt when heated

how does an earthquake early-warning system provide warning?

it detects P waves before the more damaging waves arrive

oceanic crust vs continental crust

Thickness: oceanic is 7km and continental is 35-40lm

Age: oceanic is younger than continental

Chemical Composition:

• Oceanic: Fe, Mg

• Continental: Si, Na, K, Al

  • granite upper crust and basaltic lower crust

P waves travel through _____

solides and liquids

S waves travel through ____

only solids

___ and ___ of waves reveal internal ______

refraction; reflection; boundaries

ridge push

plates slide away from elevated mid ocea ridges

• _____ proposed continental drift

• ____ proposed mantle convection as a driving mechanism

• _____ proposed seafloor spreading

• _____ mapped the ocean floor and mid-ocean ridge rift zones

• ____ used magnetic stripes confirmed seafloor spreading; youngest crust at ridges

• ____ proposed fixed hotspots and transform faults that conserve crust

• Alfred Wegener proposed continental drift

• Arthur Holmes proposed mantle convection as a driving mechanism

• Harry Hess proposed seafloor spreading

• Marie Tharp mapped the ocean floor and mid-ocean ridge rift zones

• Vine-Matthews-Morley used magnetic stripes confirmed seafloor spreading; youngest crust at ridges

• J. Tuzo Wilson proposed fixed hotspots and transform faults that conserve crust

Types of Melting

decompression, volatiles, and added heat

elastic rebound

stress builds → deformation → rupture → rebound

stress

pressure experienced by rock; strain; resulting deformation

focus

rupture origin, up to 700 km deep

epicenter

surface point directly above focus point

faults

normal = extension; reverse = compression; strike-slip = shear

body waves

through Earth

surface waves

along the surface

love

horizontal side-to-side motion

rayleigh

rolling motion—vertical and horizontal

Arrival of seismic waves

P → S → Surface

deep earthquakes have ___ surface waves

weak surface waves

Shaanxi (1556)

deadliest earthquake recorded; cave collapse

Tangshan (1976)

deadliest 20th century earthquake; collapse/liquefaction

San Francisco (1906)

fires caused about 90% of destruction

Christchurch (2011) / Haiti (2010)

contrasting infrastructure/building resilience; Christchurch liquefaction

Chile (1960)

M9.5; highest listed since 1900

Alaska (1964)

M9.2; mainly tsunami deaths

Sumatra (2004) / Tohoku (2011)

both M9.1; absent tsunami warnings versus overwhelmed defenses