Ch. 3: Earth Structure & Plate Tectonics Review

Question 1

How do you researchers know about the conditions inside Earth?

Answer 1

Researchers know about the conditions inside of Earth because of studying seismic waves from earthquakes in studying the changes in frequency and strength of the earthquakes.

Question 2

The composition/ physical properties of Earth’s crust mantle and core. Also identify continental/ oceanic crust properties.

Answer 2

Core: is thin, lightweight outer most layer.
Mantle: layer below the crust 68% of Earths mass, mainly silicon, oxygen, iron and magnesium (density is 13 g/cm^2)
Core: innermost layer, 90% iron and nickel, density is 13 g/cm^2. 31.5% of Earth’s mass.
Lithosphere: upper most cool/rigid layer of mantle -composed of cont. & oceanic crust.
Asthenosphere: Hot partially melted layer of upper mantle- extends to core.
Lower mantle: does not melt due to pressure.

Question 3

Identify continental and oceanic crust properties.

Answer 3

Oceanic crust: mostly dark colored rock (basalt) and is more dense (2.9 g/cm^2).

Continental crust: mostly light colored (granite) and is less dense than oceanic crust (2.7 g/cm^2).

Question 4

What is the isostatic equilibrium?

Answer 4

It is the balance between blocks of crust in the underlying mantle. As example, when the force of uplift or down bending exceeds the mechanical strength of the adjacent rock in some cases will cause a fault that can cause an earthquake.

Question 5

Where are you most likely to find large amounts of seismic events and volcanic activity?

Answer 5

You are likely to find large amounts of seismic events and volcanic activity at convergent plate boundary specifically around the ring of fire.

Question 6

What is the theory of plate tectonics?

Answer 6

The theory of plate tectonics is the Earths outer layers or made up of about a dozen plates floating on the asthenosphere.

Question 7

What was the contribution of Wegener and Hess?

Answer 7

Wegener proposed the theory of continental drift that Earth’s land was join together in a supercontinent called Pangaea and then started to drift apart. Hess contributed that new seafloor develops at mid ocean ridges and then spreads outwards powered by convection currents in the mantle.

Question 8

What drives plate motion/power source?

Answer 8

Convection currents in the mantle.

Question 9

Why is the core and mantle of the earth so hot?

Answer 9

It is still so hot because the pressure from radioactive decay, conduction, and convection

Question 10

What shapes most of the large scale features on Earth’s surface?

Answer 10

Continental to continental plate boundaries shapes most of the large features on Earth.

Question 11

Why is the seafloor of Earth so young while the continents are old?

Answer 11

The seafloor of Earth is surprisingly young while the continents are old because magma from the mantle is produced when the ocean plates diverges from each other causing new seafloor to be created. As the ocean plates get further away from the mid ocean ridge (where the magma was) they become more dense and subduct when converging with other plates, recycled at deep ocean trenches.

Question 12

How does paleomagnetism confirm plate tectonics?

Answer 12

Paleomagnetism confirms plate tectonics because when magma cools (magnetic small iron bearing magnetic minerals) begins to point towards earths magnetic poles. Data from the study showed that a pattern of magnetic strips were occurring on both sides of the spreading center. They showed that rocks were made at the center and then moved out words at the same rate proving that plates were diverging.

Question 13

What is a fault?

Answer 13

A fault is a fracture of rocks caused by movement of Earth’s crust which is, the force of uplift or down bending that exceeds the strength of the rock.

Question 14

What is a subduction zone?

Answer 14

A subduction zone is a place where plates subduct back into the Earth where they get “recycled” and oceanic causes islands while, continental is usually volcanoes.

Question 15

Describe and list the three types of boundaries.

Answer 15

Divergent: (create) New oceanic floor and rift valleys.

Transform: (not created nor destroyed) Earthquakes.

Convergent: (losing land being recycled) Mountains and earthquakes.

EARTHQUAKES HAPPEN AT ALL 3

Question 16

What happens when oceanic crust collides with oceanic crust; with continental crust?

Answer 16

Oceanic- oceanic: volcanoes are produced that form island arcs around the boundary and also trenches/ earthquakes.

Oceanic- continental: oceanic crust subducts in and the collision produces earthquakes, trenches, and volcanoes.

Cont. - cont.: mountains ranges formed/ earthquakes (none is subducted).

Question 17

What happens when oceanic crust diverges from another oceanic crust?

Answer 17

When oceanic crust diverges from another oceanic crust manga fills in the crustal fracture, producing new seafloor.

Question 18

What happens when a continent diverges from another continent?

Answer 18

When a continent diverge from another continent, a rift valley is formed.

Question 19

What are mantle plumes and hotspots?

Answer 19

Mantle plumes are continent sized columns of superheated mantle. Hotspots are places where molten material from Earth’s mantle reaches the lithosphere and crates volcanoes.

Question 20

What is the formation of the Atlantic ocean?

Answer 20

The Atlantic ocean formed when the single world ocean Panthalassa was separated because of the separation of Pangaea. The ocean filled in the gaps in between the African plate and the South American plate forming the Atlantic.

Question 21

What is the oceanic and continental crust made of? Also which is denser why?

Answer 21

Oceanic and continental crust are made of sediments and rocks. Oceanic is composed of mostly basalt and continental crust is made up of mostly granite.

Oceanic crust is more dense then continental crust.

Question 22

Why does the sea floor sit lower than the continents and which crust is thinner?

Answer 22

The sea floor is more dense in the continents so it’s lower. Oceanic crust is thinner (7-10 km) than continental crust (35-40 km).

Question 23

Which locations on the Earth’s crust are the thickest?

Answer 23

The mantle is the thickest location on earth even though it is dense.

Question 24

What is granite and basalt made up of?

Answer 24

Basalt- silicon, iron, magnesium and oxygen.

Granite- oxygen, silicone, and aluminum.

Question 25

When was the break up of Pangaea and what was the name of the one ocean at the time of Pangea?

Answer 25

The break up of Pangea was estimated to be about 200 million years ago and the name of the one world ocean at that time was called Panthalassa Ocean.

Question 26

What was land based evidence for plate tectonics?

Answer 26

The land based evidence for plate tectonics was that the edges of the continents fit like a puzzle, the distribution of fossils, coal deposits, and evidence of ancient glaciers.

Question 27

How fast do lithospheric plates move per year and where do you continents really end?

Answer 27

Lithospheric plates move about 2 inches per year and continents end at the continental shelf.

Question 28

What is the ring of fire, where is it located and why is it significant?

Answer 28

A basin in the pacific where many earthquakes and volcanic eruptions occur, located in the Pacific ocean. It’s important because that is where most of earths volcanoes are at because it has most of Earth’s subduction zones.