13. Earth Materials And Structure

Front 1

When seismic waves pass through rock, their amplitude and direction changes. For instance, wave velocity generally increases as rock density ______.

Back 1

increases

Front 2

The outer brittle shell of the Earth that forms the "skin" of the lithosphere. It is broken into several continental and oceanic tectonic (lithospheric) plates. These plates ride atop the more pliable mantle beneath, colliding to create great mountain systems and spreading apart to form rift valleys.

Back 2

crust

Front 3

The basal zone of the earth's crust that is primarily composed of a heavy, dark group of basaltic rocks. Primarily composed of silica and magnesium, their high density (2800 to 3300 kg/m3) is due to the large amounts of iron and magnesium.

Back 3

sima

Front 4

The less dense zone of the crust that is predominately composed of the elements silicon and aluminum. It is lighter in weight with densities around 2700 - 2800 kg/m3. Often geoscientists refer to rocks of this layer as "granitic rock" as granite is a predominant rock type.

Back 4

sial

Front 5

Layer that comprises 80% of the Earth's total volume. It is mainly composed of a dark, dense ultramafic rock called peridotite that is rich in iron and magnesium. Seismic wave velocity increases steadily through this zone. The upper portion is divided into three fairly distinct layers.

Back 5

mantle

Front 6

a rigid cool layer composed of the outer crust and the uppermost mantle.

Back 6

lithosphere

Front 7

the least rigid portion of the mantle. It is a soft, easily deformed layer that is susceptible to slow convection caused by pockets of increased heat from the decay of radioactive elements.

Back 7

athenosphere

Front 8

Separating the upper mantle from the oceanic crust is the ______ ______. Seismic waves passing though this boundary increase their wave velocity from 4 mi (7 km) per second to 5 mi (8 km) per second. The shift of wave velocity is due to the change in rock composition and density.

Back 8

Moho Discontinuity

Front 9

The rock of the oceanic crust is somewhat less dense than the mantle and referred to as _____ _____ due to the smaller proportion of iron and magnesium.

Back 9

mafic rock

Front 10

Below the asthenosphere is the rest of the upper mantle composed of rigid, solid rock called the ______.

Back 10

mesosphere

Front 11

The core is divided into the inner and outer cores. Though intense heat is generated at such great depths, geoscientists believe that under the enormous overlying pressure the inner core is made of solid ____ and ____.

Back 11

iron and nickel

Front 12

The outer core is thought to be molten ____ because shear-wave velocities drop to zero which occurs when they encounter a liquid.

Back 12

iron

Front 13

Environmental forces or processes generated by the earth's interior heat engine.

Back 13

endogenic processes

Front 14

The movement of tectonic plates is thought to be a product of...

Back 14

convection currents in the mantle

Front 15

How is heat generated within the earth's core?

Back 15

Through the radioactive decay of elements such as uranium, thorium, and potassium.

Front 16

What are the results of tectonic plate movements?

Back 16

Faulting, earthquakes, volcanoes, the creation of mountain systems, or deep valleys and trenches.

Front 17

Processes acting at the surface of the earth, primarily driven by solar energy.

Back 17

exogenic processes

Front 18

Give examples of some exogenic forces...

Back 18

erosion of surface material due to wind and rain, geologic work of glaciers

Front 19

the difference in elevation between two points.

Back 19

relief

Front 20

Relief features of the largest spatial extent. Tectonic plates are of two types, differentiated by rock and mineral composition. Continental plates are thicker and less dense, mostly composed of granitic rocks high in silica and aluminum. Oceanic plates are more dense, composed of basaltic rocks rich in magnesium and silica.

Back 20

first order relief feature

Front 21

Relief features that are the result of plate collision or divergence.

Back 21

second order relief features

Front 22

Mt. Kilimanjaro was formed as a result of...

Back 22

rifting that formed the Great Rift Valley of Africa. This is an example of rifting that is accompanied by volcanic activity as magma poured out of the rift.

Front 23

What two plates collided to form the Himilaya's?

Back 23

the Indian Plate and the Eurasian Plate.

Front 24

features that are for the most part created by erosion and deposition of the surface as opposed to the movement of tectonic plates.

Back 24

third order relief features

Front 25

a naturally occurring inorganic substance with a unique crystal structure.

Back 25

mineral

Front 26

All minerals formed by more than one element are therefore bound together by positive and negative ions. By far the most abundant ions in minerals...

Back 26

the positively charges silicon (Si) and negatively charged oxygen (O). Silicon and oxygen are the foundation of the silicate minerals

Front 27

The most important mineral family. A combination of silicon, oxygen, and another element.

Back 27

silicates

Front 28

assemblages of minerals. Unlike minerals, the composition of a particular type varies from sample to sample depending on the proportions of minerals contained within.

Back 28

rocks

Front 29

molten rock material, magma, cools (crystallization) to form ______.

Back 29

igneous rocks

Front 30

magma above the surface

Back 30

lava

Front 31

three fates of igneous rocks...

Back 31

1. remelt to again become magma.
2. become metamorphic rocks after the application of intense heat and pressure.
3. exposure to weathering, erosion and deposition to form sediment

Front 32

the fate of sediment...

Back 32

sediment may become sedimentary rock after being subjected to compaction and cementation.

Front 33

three fates of sedimentary rocks...

Back 33

1. broken down by weathering, erosion, or deposition to become sediments
2. exposure to intense heat and melting to return to magma.
3. changed into metamorphic rock

Front 34

those rocks that have been altered by exposure to heat and/or pressure.

Back 34

metamorphic rocks

Front 35

How can pressure and heat be created in the formation of metamorphic rocks?

Back 35

The pressure can be created by the weight of material lying above them. The collision of lithospheric plates creates pressure and heat that alters rock.

Front 36

fate of metamorphic rocks...

Back 36

either broken down by erosion and weathering to be deposited as sediment, or completely melted to become magma.

Front 37

Coarse-grained igneous rocks form as a result of...

Back 37

slow cooling which allows for larger crystals to form.

Front 38

Fine-grained igneous rocks form by...

Back 38

rapid cooling, usually at the surface.

Front 39

When magma intrudes into pre-existing rock it cools rather slowly because the surrounding host or country rock, as it is called, insulates the magma. As a result, crystals grow larger giving the rock mass a coarse texture.

Back 39

Intrusive igneous rocks

Front 40

The name of a rock mass of intrusive igneous rocks.

Back 40

pluton

Front 41

huge intrusive igneous rock mass or pluton that when uncovered creates topographic highs in mountainous regions.

Back 41

batholith

Front 42

Fine-grained rocks form if molten rock cools rapidly when it is extruded onto the surface.

Back 42

Extrusive igneous rocks

Front 43

such an extrusive igneous rock where there was too little time for ions to combine into an orderly crystalline structure

Back 43

obsidian

Front 44

As layers of sediment accumulate to great thickness, they are compacted and begin to harden into sedimentary rock. Each layer they form is called a bed or stratum, the process by which this occurs is called...

Back 44

stratification

Front 45

rocks that form by the compaction and cementation of sediments.

Back 45

sedimentary rocks

Front 46

The _____ sedimentary rocks form from the compaction of rock fragments, while the _____ sedimentary rocks form by the precipitation of elements.

Back 46

clastic, chemical

Front 47

a common clastic sedimentary rock formed by the compaction and cementation of sand (quartz grains).

Back 47

sandstone

Front 48

Sedimentary rock that forms from the compaction of clays,

Back 48

shale

Front 49

Sedimentary rock that forms from the compaction of silt.

Back 49

siltstone

Front 50

Sedimentary rock composed of precipitated calcium carbonate.

Back 50

limestone

Front 51

a calcium-magnesium carbonate rock that forms as a chemical precipitate or from the alteration of limestone.

Back 51

dolomite

Front 52

On land, clastic sediments consist mainly of...

Back 52

large boulders, cobbles, gravel, sand, and silt.

Front 53

On the continental shelves at the margin of continents, marine sediment is largely...

Back 53

sand, silt, and clay

Front 54

At the outer shelves and on the ocean floor, sediment is largely...

Back 54

clays and chemically precipitated calcium carbonate and the remains of tiny marine animals.

Front 55

formed by the alteration of pre-existing rocks from exposure to heat and pressure while remaining in a solid form.

Back 55

metamorphic rocks

Front 56

Metamorphism occurs in solid rock because...

Back 56

only some of the bonds between atoms are broken in an unstable mineral. As a result, the freed atoms and ions can migrate to another location within the mineral, or bond with atoms in a different mineral.

Front 57

The end result of metamorphic process is...

Back 57

to produce rocks that are more stable under the environmental conditions in which they exist.

Front 58

rocks buried deep beneath the Earth are exposed to the confining pressure created by the material that sits above a particular location, also known as...

Back 58

lithostatic pressure

Front 59

pressure along the boundary of tectonic plates where collision or subduction is occurring,

Back 59

directed pressure