Geology 1

Front 1

What is a nebula?

Back 1

Clouds of gas and dust in space that mark the birthplace of stars.

Front 2

What is the gas and dust composed of (in the nubula)

Back 2

The dust is composed of ices, oxides, carbon and heavier elements such as iron.
The gas is almost entirely hydrogen, which makes up 75% of mass in the universe.

Front 3

What does the solar nebula hypothesis propose?

Back 3

That planets were formed from the disk of gas and dust that surrounded the sun as it formed.

Front 4

What are the steps in solar system formation?

Back 4

1. slow spinning cloud of gas and dust within the milky way galaxy.
2. Nebular cloud begins to collapse. Centrifugla forces cause the cloud to collpase to a central plane which eventually becomes the plane of the solar system.
3. As cloud collpases, gravity supplies the energy to heat up and compress the center. Proto sun is formed.
4. Revolving masses of gas and dust become trapped in stable orbits around protosun.
5. Increasing heat and pressure creates nuclear fusion as hydrogen fuses into helium releasing energy and stopping the contraction. Protosun becomes true sun.
6. Within circulating rings, matter cools and starts to condense into larger particles.
7. Constant collisions cause boulders to coalesce undergravity and become smaller bodies of matter called planetesimals.
8. Planetesimals grow into protoplanets, and eventually true planets.

Front 5

What are meteorites?

Back 5

Chunks of rock or metal that fall to the earth from space. They are remnants of the primordial solar nebula.

Front 6

What are planets, moons, and space debris?

Back 6

Form as by product of star formation from nebulas. They are leftovers that didn't get incoroporated into the central star which accumulated >99% of the mass.

Front 7

How does the growth of true planets occur?

Back 7

By differentiation of materials according to density, under the influence of internal heating.

Front 8

What happens during differentiation?

Back 8

Denser material accumulates in the core while lighter material moves to the outer area.

Front 9

What happened during Earth's differentiation?

Back 9

Heavy materials like iron collpased towards the center while lighter materials such as oxygen and silicon moved to the outher surface.

Front 10

What does differentation result in?

Back 10

Most planets having an interior dense core, surrounding less dense mantle, and a thin least dense crust.

Front 11

As planets grow, where does the heat come from?

Back 11

Frictional heating through constant collision
Accumulation of radioactive elemetns that release heat as they decay.

Front 12

When did the entire differentiaon process on earth probalby finish?

Back 12

Around 4 billion years ago.

Front 13

Where did Earth's origional atmosphere come from?

Back 13

Derived by volcanism and widespread outgassing.

Front 14

What was the origional atmosphere like?

Back 14

Rich in carbon dioxide and water vapor as well as other reactive gasses.

Front 15

Where did our oceans come from?

Back 15

At some point, all of the water vapor in the atmosphere began to condense and fall as rain, thus creating our oceans.

Front 16

What is the earth composed of?

Back 16

An interior core, a thick mantle and a thin, outer crust.

Front 17

Where does the Earth derive its composition?

Back 17

Constant addition of material from the solar nebula by collisions early in its hisotry.

Front 18

What happens to pressure with increasing Earth depth?

Back 18

Increases due to the weight of the overlying rock.

Front 19

What happens to temperature as you move to the center of the Earth?

Back 19

Increases.

Front 20

The rate of change in temperature w/ depth is called..

Back 20

Geothermal gradient.

Front 21

The inner core is solid/liquid?
The outer core is solid/liquid?

Back 21

Inner core: solid
Outer core: liquid

Front 22

What is the solid inner core like?

Back 22

Almost pure crystalline iron almost as surface of the sun but frozen at the center of the planet by intense pressure.

Front 23

What is the liquid outer core?

Back 23

A dense sea of molten iron w/ traces of other metals.

Front 24

What generates the Earth's magentic field?

Back 24

The flow of liquid iron in the outer core.

Front 25

What is the mantle composed of?

Back 25

silicate rock and metal oxides that is a solid that acts like a very thick liquid. Behaves like plastic.

Front 26

What is the crust like?

Back 26

relatively thin and has the lowerst density. Composed of mostly silicate rock that acts as a brittle material.

Front 27

What is seismology?

Back 27

using earthquake waves to see inside the earth.

Front 28

What are earthquakes?

Back 28

Abrupt release of energy stored along faults in the Earth by the build up of stress along the fault.

Front 29

Why do earthquakes occur?

Back 29

When enough energy accumulates to exceed the frictional strength of the rocks on either side of the fault plane, the rocks shift abrputly, sending out seismic waves that hit the surface, causing ground shaking characteristics.

Front 30

What are the two types of body waves?

Back 30

P waves: primary/pressure wave
s waves: secondary wave or shear wave

Front 31

What are P waves?

Back 31

first wave to arrive because they travel fastest through the Earth.
Travels through solid rock and liquid material.

Front 32

What are S waves?

Back 32

secondary wave or shear wave
-slower than p waves (arrive at seismograph later)
shears rock sideways or up and down at right angles to direction of travel
-only travels through solids.

Front 33

What are the paths taken by seismic waves?

Back 33

They are not straight, nor is the speed constant. May reflect off of sharp boundaries or may refract upon contanct with a layer of different density within the earth.

Front 34

What is the speed of a wave dependent on?

Back 34

dpends on the density of the rock through which they travel. Velocity increases w/ density

Front 35

When does density and velocity of seismic waves typically increase?

Back 35

at the boundaries between each of the compositional layers in the Earth (crust/mantle boundary).

Front 36

Where do p wave velocities decrease?

Back 36

From the mantle to lquid outer core

Front 37

Another abrupt increase in P wave velocity occurs..

Back 37

at the outer to inner core transition.

Front 38

How do we know the core is mostly composed of iron?

Back 38

Iron meteorites were likely originally derived from planetesimals that had differentiated into a core, mantle and crust.
We also know that the seismic velocity of compressed iron is consitent w/ P wave velocities through Earth's core.