Unit 4.1: The Earth's Structure

Question 1

What is the geothermal gradient?

Answer 1

Temperature increases with depth as you go into the Earth.

Question 2

Why is the interior of the earth hot?

Answer 2

Radioactivity and friction

Question 3

What are the 3 main layers of the earth’s interior?

Answer 3

Core, Mantle, Crust

Question 4

Describe the core.

Answer 4

It is the inner and most dense part of the Earth, composed of nickel and iron. This is what creates the Earth’s magnetic field. Makes up 15% of volume.

Inner core: 1200 km in radius and solid due to high pressure.

outer core: 2250km in radius and liquid due to high temperature.

Question 5

Describe the mantle.

Answer 5

The middle and make up 84% of volume. 2700km is radius. Lower (inner) is plastic (solid but easily molded) and the upper (outside) part is solid.

Question 6

Describe the crust.

Answer 6

Makes up 1% of the earths volume and is the top, thin, and brittle layer of the Earth. Radius is less than 100km. Composed and different types of rocks.

Question 7

What is the lithosphere?

Answer 7

Crust and uppermost part of the mantle. It is solid and fragmented into a number of segments that move called lithospheric plates.

Question 8

What is the asthenosphere?

Answer 8

Soft, plastic layer in upper mantle that lies below lithosphere. It is what the crustal plates move on.

Question 9

What are the two types of crust?

Answer 9

Continental crust: material that forms continents. Primarily composed of granite (some aluminium and calcium), is thicker (50-70km) and less dense than other crustal layers.

Oceanic Crust: thinner (<10km) and denser. Found under major ocean basins. Mostly composed of basaltic (some iron and magnesium)

Question 10

What is mohorovicic discontinuity?

Answer 10

Boundary between crust and mantle. Depth depends on thickness of crust and crustal pressure. Average is 35 km. (continents 70km and ocean 7km)

Question 11

What are minerals?

Answer 11

Naturally occurring inorganic elements or compounds that have a definite chemical composition, physical properties, and crystal structure.

They are abiogenic (not made by organisms)

Question 12

Can the chemicals in minerals be in any order?

Answer 12

no, they have a very specific order, any changes would result in another mineral.

Question 13

What are rocks?

Answer 13

Solid mass composed of minerals or volcanic glass.

Question 14

Rocks on Earth have what 4 main minerals?

Answer 14

1. Silicates: combination of silicon and oxygen. Largest percentage of minerals in rocks 95%.
2. Oxides: other chemicals combined with oxygen
3. Sulphides & sulphates: sulphur combined with other elements.
4. Carbonates: combo of carbon and other elements.

Question 15

What are sediments?

Answer 15

Accumulations of small rock fragments and organic material that are not cemented together.

Question 16

What are outcrops?

Answer 16

Area’s of exposed bedrock typically found in environments that have significant volcanic activity.

Question 17

What are 3 types of rocks?

Answer 17

Igneous, sedimentary, and metamorphic rocks.

Question 18

What is an igneous rock?

Answer 18

cooling and solidification of magma or molten material.

Question 19

What 2 ways are igneous rocks created?

Answer 19

1. decompression melting; melting of hot mantle material as a result of pressure changes.
2. Flux melting: lowering of melting point of material due to the addition of subjected water.

Question 20

What is the difference between intrusive and extrusive igneous rocks?

Answer 20

Intrusive: the cooling of molten material under the surface.

Extrusive: the cooling of molten at the surface.

Question 21

what is exhumation?

Answer 21

the removal of overlying rocks sediments to expose deeper rocks.

Question 22

What 5 different formations can occur with the formation of igneous rocks?

Answer 22

1. Pluton: dome-shaped igneous rock mass up to a few tens of kms in diameter.
2. batholith: massive, dome-shaped, igneous rock that has melted and assimilated to most the existing rock structure it has evaded.
3. Sill: formed when magma inserts itself as a thin, horizontal layer between strata of existing rocks without disturbing older layers.
4. dike: similar to sill. forms vertical sheet of igneous rock.
5. Laccolith: Dome-shaped igneous rock body that is formed when a magma pipe leads into a chamber in the rock. Magma pushes the overlying strata into a gentle budge without destroying the strata.

Question 23

What are sedimentary rocks?

Answer 23

composed of sediments that have been compacted and cemented into new rock.

Question 24

What are the 3 types of sedimentary rocks?

Answer 24

1. clastic: composed of broken pieces of other rocks
2. Organic: composed mostly of organic material from dead ancient organisms.
3. Chemical: formed from dissolved minerals that are precipitated out of water.

Question 25

What are the 3 most common sedimentary rocks that make up 99% of all sedimentary rocks?

Answer 25

shale (45%), sandstone (32%), and limestone (22%)

Question 26

What are metamorphic rocks?

Answer 26

formed from other rocks that have been modified under high pressure and or temperature. they are mostly formed deep below the surface and are the least common exposed rock.

Question 27

What are 2 categories of metamorphic processes that convert rock form?

Answer 27

1. contact metamorphism: rocks come into contact with and is heated by magma. More local version
2. Regional metamorphism: heat and pressure found when two crustal plates converge. More regional version.

Question 28

What are 2 main groups of metamorphic rocks?

Answer 28

foliated: flat or wavy banding patterns, they are formed by compression.

non-foliated: no pattern to grain or minerals, formed when heat and pressure are applied equally.

Question 29

What is the rocks cycle?

Answer 29

describes formation and transformation of rocks from one type to another. they are constantly changing and it is a closed cycle.