Earthquakes and Volcanoes Test 1

Age of Life?

3.5 BY

Age of the Earth?

4.6 billion years

When did Dinosaurs Die?

65 Million Years Ago

A review of basic ideas about the interior of the Earth is like _________

A chili pot

Listric Fault

A normal fault that flattens with depth and typically found in extensional regimes. This flattening manifests itself as a curving, concave-up fault plane whose dip decreases with depth.

Earthquake after small earthquake is called:

Aftershock

What is the Law of original horizontality?

All sedimentary rocks form horizontally. If not horizontal-they moved somehow.

What are the two types of Seismic waves?

Body Waves and Surface Waves Body waves go through the volume of the Earth; Surface waves go along the surface of the Earth

Which of the two Seismic waves are faster?

Body waves are faster than surface waves

Rocks can either be:

Brittle • Break along faults Ductile • Deform without breaking

What are the layers of the Earth

Crust, Mantle, Outer Core, Inner Core

Rupture has a propagating front that moves:

In a particular direction really fast

Rupture has an origin, called a _________________

Nucleation point

Omori's law

Number of aftershocks per day varies inversely with number of days after main shock

What controls the size of an Earthquake?

The eventual size of the earthquake is a consequence of the rupture process

Snell's Law

A formula used to determine the angle at which light will refract from one medium to another

How was the moon created?

A very large object collided with earth, causing earths outer layers flew into space. Because of earths gravity, the materials orbited earth and came together to form the moon

How many earthquakes per year?

About 3 mill

Who came up with the Continental Drift?

Alfred Wegener

Elastic Rebound Theory

The theory that continuing stress along a fault results in a buildup of elastic energy in the rocks, which is abruptly released when an earthquake occurs.

What is a Fault?

An earthquake is understood as a consequence of an abrupt motion of rock masses along a planar surface called a "fault"

Rutgersium decays exponentially with time, it has a half life of 17 years, it's daughter product is Princetonium. You find a fossil with 125grams of Rutgersium and 875grams of Princetonium. How old is the fossil?

Answer: First Cycle: 17 years = 250grams Rutgersiums 750grams Princetonium Second Cycle: 34 years = 500 grams Rutgersium 500 grams Princetonium Third Cycle: 51 years = 1000 grams Rutgersium 0 grams Princetonim.

Why does Earth have layers?

Basics of Earth Formation Theory Why does Earth have layers? Step 1: A lot of small particles of material, both rocky and metallic, accrete into a proto-planet Step 2: The proto-planet warms up heating by impacts heating from radioactive decay Step 3: Material forming the proto-planet melts release Step 4: Resulting layered structure progressively cools

Why is Earth uneven?

Because it spins! The axial dimension is smaller then the equatorial. Over a very long time Earth's material is similar to a liquid

What is Density?

Density is the ratio of the mass of an object to the volume it occupies. D = mass/volume

Who first associated earthquakes with geological faults.

Edward Seuss (1875)

True or False: all faults are on plate boundaries

False; Not all faults are on plate boundaries

Ground Motion

Familiar trembling and shaking of the land during an earthquake which causes a lot of damage

Fast movement on a fault is called

Fast movement on a fault is called slip - causes earthquakes - repeated episodes of slip on the same fault are referred to as stick-slip behavior

Planar fault

Faults as parallel cracks and as they break away they are like dominoes and fall over.

Focus vs Epicenter

Focus: -The place where the motion takes place is called a source or a focus or a hypocenter of an earthquake. The "earthquake" in the context of this class will be the process in the source. Epicenter -The place where energy from the source reaches ground surface is called the epicenter.

Rupture parameters are controlled by:

Forcing Resistance

________ makes materials behave in plastic manner. Including rocks.

Heat

Who came up with the Elastic Rebound Theory?

Henry Fielding Reid

The Law that describes the Elastic Rebound Theory is called what?

Hooke's Law Hooke's Law (for a linear spring): F = X * K F = force X = distance of deformation K is called the force constant

Why do we care whether a fault is right or left lateral? Why do we care which wall is the hanging wall and which is the foot wall?

If you know whether a fault is right or left lateral, you can tell which direction the ground is being pushed. If you know which wall is the hanging wall, you can tell if the fault is normal or reverse and whether there is extension or compression.

The core is made of _________

Iron

Continental crust is lighter, on average made of ________

granite

The rock forming the mantle is called _______ The main mineral in this rock is called _______

peridotite olivine

Transform boundaries

plates slide past each other causes earthquakes (ex: San Andreas Fault)

The longest period radiated is ______________ to the size of the fault that moves.

proportional For larger earthquakes more energy goes to waves with longer periods

An episode of slip on a fault is called a __________

rupture

A surface of the fault (especially when exposed) is known as a

scarp

What are the two types of strike slips?

Left-lateral (down, up) ; Right-lateral (up, down)

half life

Length of time required for half of the radioactive atoms in a sample to decay

Fermat's principle

Light rays will take the quickest path

Crust and the upper part of the mantle form the _____________________

Lithosphere - a stiff outer shell of the planet. Lithosphere MOVES with respect to the rest of the planet

To measure an earthquake we have to use which formula?

M0 =μAD=μ*L*W*D

An earthquake that follows a large earthquake is called

Mainshock

Difference between P Wave and S Wave?

P Wave: Pressure Primary Straight P waves travel faster than S waves S Wave: Shear Secondary Curvy

What is the time period of the waves?

P waves arrive first Then S waves Then Love waves Then Rayleigh waves

What are the two types of body waves?

P-Wave and S-Wave

Difference between Period, Amplitude, and Wavelength

Period: Time between waves Wavelength: Actual distance between waves Amplitude: Height of waves

What is the fault here in NJ called?

Ramapo Fault

What is the Principal of superposition?

Rocks on top are younger than those on the bottom

When a fault moves it can experience:

Rupture (and make an earthquake) Creep (and do not make an earthquake)

Units for density: Solids: Liquids: 1cm3 =

Solids: g/cm3 Liquids: g/mL 1cm3 = 1 mL

Continental Drift

The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations

How Faults Make Earthquakes?

The rupture process Earthquake sequences

Measures of earthquake size

- Magnitude - Seismic Moment - A Moment Magnitude

Earthquakes and Volcanic eruptions are by-products of two large-scale processes?

- Mantle Convection - Plate Tectonics

When a ray comes to a boundary between two materials, it can:

- Reflect (I.e. bounce back into ‏)material it came from - Refract (I.e. go from one material to

A magnitude is defined for:

- a fixed distance - a specific wave - a specific recording instrument

Age of "Real" Life?

1 BY

Asthenosphere

The solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it The solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it

What are some Deformation Types?

There are three types of deformation... 1. Plastic - Material flows and retains the shape that it is bend into. Wet Clay. 2. Elastic - Material bends but returns to original form once stress is removed. Wood. 3. Brittle - Material breaks under stress. Glass.

What is a Moment?

Total amount of energy released at the source

True or False: As you move closer to the center of the Earth the densities of the layers increase?

True

True or False: Not all faults are active

True • Active fault - a structure that shows current/recent movement • Inactive fault - a plane or a zone separating different rocks, but with no evidence for activity • Faults may become reactivated

What are the questions that can used to ask to find the location of a earthquake?

Where & When? How Big? Was it a nuke?

What if plates meet?

Where two plates come together the lithosphere is destroyed. - "destructive margins" • One plate goes under the other - subducts - Subduction zones

Mantle Convection

a recurring current in the mantle that occurs when hotter, less dense material rises, cools, and then sinks again. This current is believed to be one of the driving forces behind tectonic plate movement.

We currently in the _______ time period a) Cenozoic b) Mesozoic c) Paleozoic

a) Cenozoic

What is a dip?

an angle from the horizontal that is measured along a direction perpendicular to the strike

Oceanic crust is denser, made largely of a rock called ________

basalt

Slow continuous movement on a fault is called

creep or stable sliding -Does not cause earthquakes

Most rocks masses behave _______________.. Meaning they bend. Up to a point. Then they break.

elastically

The concept of magnitude is based on __________ in propagating waves

energy loss The concept of magnitude is based on energy loss in propagating waves: - Amplitude of seismic waves decreases with distance from the source Different sizes of earthquakes make different waves, but rate of amplitude decrease with distance is the same

If a small earthquake is followed by a larger earthquake nearby - the small one is called a _________

foreshock

Earthquake magnitude is a _________ measure

logarithmic

An interface between two plates where earth quakes take place is called a _____________

megathrust

What is a strike?

orientation of a line where the plane intersects the surface, in degrees clockwise from North

Conditions for rupture:

something has to break

What is Relative age?

the age of a rock compared to the ages of other rocks

What are Divergent margins?

the earth is ripped open, and magma flows up through it; like a cut.

Absolute Age

the number of years that have passed since the rock formed

Plate Tectonics Theory

the theory that the earth's crust and upper mantle consist of huge plates slowly drifting as a result of convection currents in the mantle'

What are Seismic Waves?

vibrations that travel through Earth carrying the energy released during an earthquake

A _____ transports energy, not material

wave

Observations from 1906 San Francisco earthquake:

• A long trace of ground breakage - A fault • A very large lateral offset - 6.5 meters • Availability of recent land surveys showing that the ground was deformed over a period of time preceding the earthquake

Hanging Wall vs Footwall

• Hanging wall is above the scarp • Footwall is below the scarp

What are the two types of Surface Waves?

• Rayleigh Wave - A combination of vertical and horizontal motion • Love wave - Horizontal motion • Amplitude of motion in surface waves from a typical earthquake is larger then in body waves

An earthquake of a given magnitude is _________ smaller, and takes place __________ as often, as an earthquake of the next size up

10 times 10 times

When did Humans appear?

200,000 years ago.

Water has a density of ____________

1.0 g/mL

Where did the first earthquake that revealed faults occur?

Mino-Owari, Japan earthquake, Oct. 28, 1891

What did Mohorovicic observe?

Mohorovicic observed an abrupt change in seismic wave speed at a certain distance from the earthquake source, regardless of direction. Postulated the idea that the Earth is covered by a layer of low-speed material, and has higher-speed material at depth.

Moment vs Magnitude

Moment: Based on mechanics of fault Often measured remotely Inconvenient for public use Lots of assumptions required Moment is a quantity computed according to mathematical expressions describing physical reality... Magnitude: Based on ground shaking Measured locally Convenient for public use Lots of assumptions required Magnitude is a "rule"-based measure I.e. "wave A of period B at distance C means there was an earthquake of magnitude M" No specific physics...

When measuring earthquakes you are looking at:

Need to measure the size of the source of energy A measure based on what is happening at the source is called a seismic moment A measure based on observations of ground shaking (seismic waves) is called a magnitude

3 main types of faults

Normal Reverse Strike Slip