Geoscience In movies - exam 1

Know Earth’s four layers

The crust (solid)

mantle (solid)

outer core (liquid)

inner core (solid).

How the Earth acquired its internal heat.

Small particles collide with each other, the more they collide the more they form a larger body. Swipe up large bodies of gas and form more. The temperature of the particles increases. The inside of the planet melts, material sticks to the center.

Planetary accretion

the clumping of mass and particles due to gravitational pull

Radioactive decay

is what leads to internal heat. Heavier materials sink to the bottom

WHY is the interior of the Earth layered?

Due to the manner of it’s formation and planetary accretion.

• Heat of collisions +radioactive decay leads new planets to be molten/melted inside, which leads to differentiation as heavier elements sink to form a core and lighter elements rise to form a crust and mantle.

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

• The inner core which is made out of nickel and iron are under a lot of pressure which solidifies them.

• The outer core remains liquid because it is above

Lithosphere

outer shell of the Earth consisting of the crust and coldest, stronger layer of the mantle

• Can break but does not readily flow.

• Breaks into separate plates (plate tectonics.)

Asthenosphere

• Weakest layer of the mantle

• (flows readily) It can flow like a fluid but it is a solid (kind of like silly putty)

• allows tectonic plates to slide around the surface of the Earth.

What is the evidence that Wegner used to suggest that the continents drift?

Fit of the continent’s shape

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

Fossils of non-swimmers found on both sides of the modern oceans

Similar type of lava flow on different continents

NOT one of the main types of data: the age of rocks on each continent

Magnetism

a force produced by the motion of electrons, resulting in attractive and repulsive forces between objects.

• Emphasized with coils. Coils get empowered around metal objects like iron

The components required for Earth’s magnetic field

• Dynamo - process of liquid iron acting as elongated coils

• Earth’s liquid Iron outer core provides all components necessary for a strong magnetic field

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

• Magnetic field can flip, as seen through magnetic stripes in ocean floor

• A magnetic field can be visualized by its field lines.

What is mid-ocean ridges, subduction zones, and transform plate boundaries?

• Mid-ocean ridge: (divergent boundary)

Plates move away, where new lithosphere ocean plate is created

• Subduction Zone: (convergent boundary)

Plates move towards each other, where one plate gets subducted under another. The oceanic crust sinks beneath the continental crust due to density.

Subduction zones are where most earthquakes and volcanoes occur

Most dangerous of all plate boundaries (most earthquakes, largest earthquakes, most volcanoes)

• Transform boundary

Two plates move (SLIDE) past each other (san Andreas fault

What is a passive plate margin?

when a boundary between continental crust and oceanic crust is not a plate boundary

What is a supercontinent?

A massive landmass that contains multiple continents joined together

• Pangea is the most recent one

What caused the high topography of the Himalayas and Tibet? 

Caused by: the ongoing collision between the Indian and Eurasian tectonic plates

Converging of the two plates forces the mountain range to continue to thicken and float on the surface

• Isostasy (the floating) and is similar to how icebergs float

What is the Wilson cycle?

The Wilson Cycle describes how continents break up and then rejoin and the life cycle of ocean basins

Can convection occur within a crystalline solid (Earth’s Mantle)?

Yes, convection can occur in the mantle because the high temperature and pressure allow the solid material to flow slowly over time.

Mantle convection (main source of plate movement):

slow, circular movement of earth's mantle, in which heat causes the mantle to "recycle"

• Plate creation (ridge push): occurs at ridges (diverging plates)

• Plate recycling (slab pull): occurs at subduction zones (converging plates)

The consequences of losing our magnetic field:

• Losing magnetic field would weaken the atmosphere

• Exposing us to solar winds (deadly charged particles from the sun)

• Radiation

• Harm to satellites, navigation systems and power grids due to there not being a N or S pole

The largest earthquakes to occur in the past 100 years

• Chile; 1960, 9.5, 11 minutes.

• Alaska; 1964, 9.2, 5 minutes

• Sumatra; 2004, 9.1, 5 minutes

• Japan; 2011, 9.0, 6 minutes. Moved a portion of Japan 8 feet.

• Kamchatka, 1952, 9.0, 4 minutes

What is elastic rebound and stick-slip behavior?

Two processes describe the earthquake cycle:

• Elastic-rebound: the crust bends like rubber (storing energy), then unbends (releasing energy).

• Stick-slip behavior: faults remains stuck while energy builds, then suddenly slips when energy is released

What is asperity ?

Rough spots along the fault that prevent the fault from sliding until they are broken

Locked patch on a fault storing strain. ( The earthquake rupture usually begins at an asperity.)

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

Before: Plates lock, crust bends and stores energy

During: Plates slip suddenly releasing energy → uplift and cause tsunamis

What is the type of plate boundaries and direction of relative plate motion in which thrust, normal, and strike-slip faults occur?

• Thrust faults - COMPRESSION /convergent / subduction zones

Hanging walls go up. Footwall goes down.

• Normal faults - EXTENSION /divergent

Hanging walls go down. Footwall goes up.

• Strike-slip faults - SHEAR/ transform

Horizontal motion along the ground.

How do movies generally and incorrectly depict earthquakes?

• large sinkholes

• Last really long, but in reality, the large earthquakes last only a few minutes at most.

Two Types of Body seismic waves:

P primary wave: Push/pull

• travels through the Earth

• moves through liquids, gases, and solids.

• first to arrive.

• Push-pull motion.

• Compressional waves particles move along the direction of propagation.

S secondary waves: Snake

• travel through the Earth

• move through only solids.

• The second to arrive.

• Up and down motion.

• Shear waves particles move perpendicular to the direction of propagation.

Two types of Surface Waves: SLOWEST AND MOST DAMAGING

Love Waves:

• A surface wave that travels along the surface of the earth

• Side to side motion (cause the most damage)

• Before rayleigh

Rayleigh waves:

• A surface wave that travels along the surface of the earth

• Up-down rolling motion (like an ocean wave)

• Last of the waves to arrive

How many seismograms are required to locate an earthquake

Three

Triangulation:

D = V/T

Using the time between the P-wave and S-wave the distance/location of the earthquake can be determined

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

S waves do not travel through the outer core and P waves slightly deform/reflect when traveling through changing materials.

How are earthquake magnitudes related to the relative magnitude of shaking?

Earthquake magnitude is a logarithmic scale; for every whole number increase in magnitude, the amplitude shaking goes up by a factor of 10

Shaking from M6 is 10x greater than M5

Shaking from M7 is 100x greater than M5

Shaking from M8 is 1000x greater than M5

Maximum magnitude?

Maximum magnitude of an earthquake is M10; an M10.5 earthquake is theoretically impossible

What’s the influence of loose sediments on earthquake shaking 

Loose sediments: Amplify shaking — more damage in soft soil areas

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

• Based on self reports

• Can be used to estimate the size of historic earthquakes

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

Earth’s crust is stronger + less fractured (less active faults) in the East, allowing seismic energy to transmit better

Biggest vs deadliest earthquakes

Biggest earthquakes:

• Largest stress build up

• Longest faults

Deadliest earthquakes:

• Largest populations

• Bad building practices

Why are earthquakes difficult to predict?

Stress builds slowly and release timing is unpredictable

What forecasting earthquake probabilities is based on

Slip deficit rates and time since the last earthquake.

The problem with earthquake precursors

There are no reliable earthquake precursors at the moment. Events like foreshocks or unusual animal behaviors are inconsistent, and can occur without following a major earthquake.

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

Knowing the slip deficit rate and time since the last earthquake occurred helps forecast the potential size of the next earthquake.

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

Historical data of 3 of the largest earthquakes that occurred in New Madrid or the midwest.

Things to do to minimize earthquake deaths, especially your own

If indoors (in a developed country):

Stay inside; drop, cover (under table), hold on; use doorway for shelter ONLY if it’s a strongly supported, loadbearing doorway; avoid elevators

If indoors (in a 3rd world/developing country):

Get out of the building as fast as possible.

If outdoors:

Stay outdoors and move away from buildings.

Why diagonal beams help buildings be more resistant to earthquakes

Diagonal beams provide resistance to shearing that often causes buildings to collapse.

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

90% chance of avoiding total collapse. That means 10% of buildings could collapse during the next major earthquake.

The importance of a proper foundations and what liquefaction is

Liquefaction is a process in which a saturated or partially saturated soil substantially loses the strength and stiffness due to an applied stress as shaking during an earthquake.

Buildings can fall over during an earthquake due to liquefaction, where shaking temporarily turns wet sediments into a fluid.

How we can keep a building from swaying too much during an earthquake

Concrete floors are incredibly heavy and without proper steel reinforcement and lateral support, it can lead to a building to pancake during an earthquake.

Diagonal beams provide resistance to shearing that often causes buildings to collapse.

Base isolation systems decouples a building from its foundation, allowing it to move independently during an earthquake.

Inertial Damping Systems, counteract the movement and reduce overall motion

How do earthquake early warning system work?

Seismic waves travel slower than the speed of light. Therefore, one can detect an earthquake and communicate a warning ahead of the shaking. (on phone)