Geoscience in Movies Exam 1

Know Earth's layers and their approximate relative's thickness

Crust: Low density, cold, strong rocks, solid

7 km beneath oceans

40 km beneath continents

70 km under mountains

Crust in the ocean is called oceanic crust

Mantle: higher density, hotter rocks beneath crust, solid

2900 km

The mantle is divided into several layers because of heat/pressure (with different chemistry densities and strengths)

Lithosphere: strong and brittle (broken into a number of plates)

the combination of the crust and upper mantle

Asthenosphere: the weakest layer of the mantle and underlies lithosphere

It flows like a liquid, but it's solid (silly putty)

Outer core: 2200 km (liquid)

Liquid due to high temperature and not enough pressure

Inner core: 1200 km (Solid)

How the Earth acquired its internal heat

Multiple collisions during formation. Radioactive decay. Iron sinks to the core heavier in the center and lighter elements in the crust.

Know why the interior of the earth is layered

Because of how it was formed (planetary Accretion). Heat from collision and radioactive decay leads new planets to be molten inside, which leads to differentiation in heavier elements to sink to form core, and lighter ones to rise

Why the outer core is liquid, but hotter inner core is solid

The inner core is under more pressure

Outer core is liquid because it melts. Also due to high temperature and not enough pressure (Materials like iron sink into the inner core because its heavier)

What Lithosphere and Asthenosphere are

Lithosphere: strong outer shell of the earth. It is a combination of the crust and upper part of the mantle. It can break into separate plates (plate tectonics)

Asthenosphere: Flows like a liquid but it's solid (silly putty). It flows under the Lithosphere. It's the weakest part of the mantle and so it allows the movement of the lithosphere

Know the evidence that Wegner used to suggest that the continents drift

America and continents on the other side of the pacific ocean fit together

Fossils of non-swimming animal on both sides of the modern ocean

Glacial striations were lined up and they looked to be continuous across continents

Drastic changes in climate in the same location over time

(coastlines fit)(glacial striations were lined up)(fossils of nonswimmers)

When glaciers form they tend to move and they create marks

You could put them back together

Looked at lava flow for similar rocks in continents

Fossils found of nonswimmers

How we know that our magnetic field has reversed itself many times

Through the orientation of iron minerals that cooled down in molten rock happened at mid ocean ridge magnetic reversals are recorded in lava flows by magnetic crystals, which show them to have occurred throughout earth's history

Examining magnetic charges of rocks

What's a mid-ocean ridge, a subduction zone, and a transform plate boundary

Mid-ocean ridge: At the mid-ocean ridge new crust is formed at the ridge and the convection cells push them away from each other and the old crust will get destroyed at the subduction zone (magnetic lineation on the sea that show how oceanic crust is created, it is where new plates are formed.)

Subduction zone: it is where old oceanic lithosphere (including crush) descend (subducts) beneath continental or other oceanic lithosphere. Most earthquakes occur. Plates get destroyed in the subduction zone

Transform plate boundary: (nothing is formed or destroyed) slide past each other either left or right. Highly fractured fault zones at the constant points Sometimes called strike slip

What's a passive plate margin

Boundary between continental crust and oceanic crust (not a plate boundary)

A passive margin is the transition between oceanic and continental lithosphere that is not an active plate margin

What's a supercontinent

Pangea (when all the continents were together)

What caused the high topography of the Himalayas and Tibet

From collision of India into Eurasia - a convergent boundary collision

The only place where two continents are colliding (colliding creates mountain ranges)

What's the Wilson cycle

Describe how the continents break up and rejoin again

(new oceanic crust, plates will start to subduct and plates will start to collide, creating mountain ranges)

Breaking of continents and rejoining

Whether convection can occur within a crystalline solid

Yes in the case of the mantle, where convections occur and drives plate tectonics

What drives plate tectonics

Convection on the earth's mantle

The components required for earth's magnetic field

Rotation of the earth creates the liquid to act like a coil, the electrical current come from the motion

The consequences of losing our magnetic field

Auroras would be visible every night, more charged particles would reach earth causing power outages, Migratory animals would have trouble guiding themselves (bird, turtles, bees), no mass extinctions, compasses would go crazy

The largest earthquakes to occur in the past 100 years

Chile 1960, magnitude 9.5, lasted 11 minutes

What elastic rebound and stick-slip behavior are

Elastic rebound: crust bends like rubber (storing energy) then unbends. Occurs because of friction

Stick-slip behavior: faults remain stuck while energy builds, then suddenly slips when energy is released. So when a earthquake happens it bends back to it rebonds back to its original shape

What's an asperity

Rough spots in the fault. It's an area on a fault that is stuck, the earthquake rupture usually begin at an asperity

As asperity is an area on a fault that is stuck. The earthquake rupture usually begins at an asperity (they just cause resistance and as the plates move they break)

How do the plates deform before compared to during a subduction zone earthquake

The setting (type of plates boundaries, direction of relative plate motion) in which thrust, normal, and strike-slip occur

How movies generally and incorrectly depict earthquakes

Movies show a gap in the earth when earthquakes occur. In reality there are no gaps after earthquakes

The types of seismic waves and their basic properties

-body waves: travels through body of earth; through inner layers

- 1. P-WAVES: P-waves (primary or pressure): a body wave that travels thru the earth

push pull motion (compresses and expands like a sound wave)

Travels thru solids solids liquids and gases

Fastest seismic waves (first to arrive), shake up and down bc it moves directions of propagation, waves come from below, vertical, only feel up and down movement

Compressional waves: particles move along the directions of propagation

2. S-WAVES: secondary or shear: a body wave that travels thru the earth, up-down, or side to side motion (shear), will not travel thru liquid, slower than p-waves (second to arrive)

Shear waves: particles move perpendicular to the direction of propagation

Vibration is side to side, perpendicular to direction of propagation (up and down)

SURFACE WAVES: travels close to the surface, cause most damage, undulating movement, travel across thru surface, slowest,

1. LOVE WAVES: a surface wave that travels along the surface of the earth, side to side motion, along the Rayleigh waves, they are the last to arrive but cause the most shaking, weighs die out with depth

2. RAYLEIGH WAVES: a surface wave that travels along the surface of the earth, Up down (rolling) motion like an ocean wave, along with lovewaves, they last to arrive but cause the most shaking

How many seismograms are required to locate an earthquake

Three (trinaglifocation)

How we know the outer core of the earth is liquid and the inner is solid

Beno Gutember discovered the earth's outer core was liquid from s-waves shadow zone (in this area s-waves cannot be registered)

Inge Lehmann discovered the earth's solid inner core from deflections of P-waves at the inner core/outer core boundary

b/c inner core is under more pressure

The outer core is not under enough pressure to be solid and due to the density of rock it can handle more heat

How earthquake magnitudes are related to the relative magnitude of shaking

Magnitude based on the extent of the area on the fault that slipped and the amount it slipped. The duration of shaking increases with earthquake magnitude.

(The earthquake magnitude is logarithmic scale: for every whole number increase in magnitude, the amplitude of shaking goes up by a factor of 10.)

The theoretical maximum earthquake magnitude

M= 10, limit to how big earthquake can be

The influences of loose sediments on earthquake shaking

Causes greater damage on structures above it

What earthquake intensity (Mercalli Scale) measures and the factors that influence it

The amount of shaking felt by people and buildings during an earthquake

Why earthquakes are felt father away in the eastern US compared to the western US

Shaking more intense in east because the crust is stronger and less fractured and transmits seismic energy better

Used to the elastic rebound in the west

Shaking is more intense in the East because the crust is stronger and less fractured (less active faults breaking it up) and transmits seismic energy better

The relationship between the biggest magnitude earthquakes and the deadliest

Just because an earthquake is a high magnitude 8.0+ doesn't mean it's the deadliest. It is completely reliant on placement, more populated areas are going to have more destruction than if it had the same magnitude as an earthquake in the middle of the ocean. It depends also on the depth of the earthquake, one that formed deeper in the earth and one that is closer to the surface is going to have a different intensity of shaking felt by people and destruction

Why earthquakes are difficult to predict

Time magnitude of earthquake on any faults are highly variable making them impossible to predict (where, when, how big)

1. Rate at which stress builds on faults, Level of stress that will cause a fault to slip, Stress released on the fault during an eq ALL HIGHLY VARIABLE!!!!

2. Best chance at predicting eq= discovering . a precursor(observable process that always precedes an eq)

The time and magnitude of earthquakes on any fault is highly variable, making them impossible to predict

Stress does build uniformly, stress limits vary between faults, cannot directly measure stress on faults

What forecasting earthquake probabilities is based on

Foreshocks, Changes in ground elevation, Locations of seismic gaps along a fault

The problem with earthquake precursors

They aren't reliable

How GPS is used to predict how big the next earthquake in a region is likely to be

GPS measurements enable us to measure slip-deficit rates + amt an earthquake will need to slip in order to reduce elastic stress build-up

Why the US Geological Survey believes there is a high seismic hazard in the midwest

3 of the largest earthquakes to occur in . the contiguous US has happened in the Midwest

Things to do to minimize earthquake deaths, especially your own

Educate people on what to do during an earthquake

Enact building codes for new construction

Retrofit old buildings

Legislate strict building codes that require strong and flexible buildings.

Do not build near active faults, especially on loose soil

Develop earthquake early warning system

Why diagonal beams help buildings be more resistant to earthquakes

Diagonal beams provide resistance to shearing that often causes buildings to collapse; compression of one diagonal (gets shorter); extension of the other (gets longer)

The percent chance of avoiding collapse during an earthquake that California building codes require

10% max

The importance of a proper foundations and what liquefaction is

Building can fall over during a quake if not properly anchored ; can fall over due to liquefaction where shaking temporarily turns wed sediments into a fluid

process by which water-saturated, unconsolidated sediments are transformed into a substance that acts like a liquid often in an earthquake

What forced resonance is and how we can keep a building from swaying too much during an earthquake

Forced resonance: Occurs when the natural frequency of a structure matches the frequency of external forces (freq. Of the ground during a eq) → structure suffers severe damage + possible collapse approaches to reducing the swaying of building

Base isolation systems 2. Inertial damping systems

How an earthquake early warning system works

Seismic waves travel slower than the speed of light, therefore, one can detect an earthquake and communicate a warning ahead of the shaking