Geology Test 3 // Chapter 9

Front 1

Core-mantel boundary lies at a depth of about

Back 1

2,900 km.

Front 2

Gravity is measured using a

Back 2

gravimeter.

Front 3

Gravimeter: definition

Spring _____ if the local Gravity is high and _____ if local Gravity is low.

Back 3

measures the gravitational attraction between the Earth and a mass inside the gravimeter. spring *lengthens* the local gravity is high and if the spring *shortens* then the local gravity is low.

Front 4

Geothermal gradient ____ in temperature with length.

Back 4

increase in temperature with length

Front 5

In crust the geothermal gradient is ____ and in the mantle it is _____.

Back 5

25 degrees C per km // 1 degree C per km.

Front 6

Why is geothermal gradient higher in crust?

Back 6

b/c of its abundance of radioactive decay.

Front 7

Stress is _____ divided by _____.

Back 7

force divided by area.

Front 8

Compressive stress is when rocks have undergone _____.

Back 8

rocks have undergone shortening

Front 9

Tensile stress: rocks have been _____.

Back 9

rocks have been stretched

Front 10

stress acting parallel to a plane like the shearing of a deck of cards

Back 10

shear stress

Front 11

During Deformation, rocks can undergo one or more of the following

Back 11

1) a change in location (displacement) 2) a change in orientation (rotation) and 3) a change is shape (distortion, aka strain)

Front 12

Rock stretches or contracts as stress is applied and returns to its original shape when the stress is turned off (behavior at low stress levels). – Passage of seismic waves

Back 12

Elastic behavior

Front 13

Rock breaks when stress is applied. Typical of near surface (shallow) behavior; in general, b/c the temperatures are cooler at surface when the temperatures are lower).

Back 13

Brittle behavior

Front 14

when a rock permanently deforms as the stress is applied. Objects change shape without actually breaking. Occurs at depth within the Earth. Many bonds break but new ones quickly form. In this way, the atoms within grains rearrange, and the grains change shape without permanent cracks forming.

Back 14

. Ductile behavior.

Front 15

Line of intersection between a tilted planar bed and a horizontal plane. A horizontal line where a bedding plane intersects a horizontal surface (expressed as compass direction).

Back 15

Strike

Front 16

the angle in which the planar object dips into the Earth. The compass direction of a rock layer that is tilted downward from a horizontal plane.

Back 16

Dip

Front 17

Direction of Dip is always ___ degrees from or perpendicular to the direction of the strike

Back 17

90

Front 18

The vertical angle between the horizontal plane and the bed measured in degrees

Back 18

Angle of dip

Front 19

Geologist use a _____ to measure strip and dip.

Back 19

Brunton Compass

Front 20

Elastic strain occurs when rock ____ to its original shape after a stress is ____.

Back 20

Returns // relaxed.

When a rock is stressed beyond its elastic limit, it will bend and not regain its original shape.

Front 21

Plastic strain occurs when a rock ____ in the form that stress creates rather than returning to its original shape.

Back 21

Remains

When a rock reaches its plastic limit, it breaks.

Front 22

Fractures with rock displacement are called

Back 22

faults.

Front 23

Fractures without rock displacement are called

Back 23

joints.

Front 24

undulations (waves or bends) that form in rocks when the earth’s crust is strained to its plastic limit by stress related to tectonic activity.

Back 24

folds

Front 25

______, __________, and _________are found in fractures and folds.

Back 25

Oil, gas, and minerals

Front 26

beds arch with their convex side up. Oldest layers are in the middle

Back 26

Anticline

Front 27

beds arch concave side up. Youngest layers are in the middle.

Back 27

syncline

Front 28

an anticline that is circular or elliptical in shape

Back 28

Dome

Front 29

A Synclinebeds that is circular or elliptical in shape

Back 29

Basin

Front 30

a local steepening in an otherwise uniform and gentle dip

Back 30

Monocline

Front 31

A fold with a vertical axial plane. Its two fold limbs dip in opposite directions at the same angle.

Back 31

Symmetrical fold

Front 32

fold with a dipping or inclined axial plane. Its two fold limbs dip in opposite directions with one limb dipping at a steeper angle than the other.

Back 32

asymmetrical fold

Front 33

A fold with an axial plane that is drastically inclined from the vertical position to the degree that its two fold limbs dip in the same direction

Back 33

overturned fold

Front 34

As fold with a nearly horizontal axial plane. _____ meaning lying down.

Back 34

Recumbant fold

Front 35

A fold with both limbs that dip at the same angle.

Back 35

Isoclinal fold

Front 36

A fold with a horizontal axis. Its limbs’ beds strike in the same direction. A series of ______ folds shows parallel outcrop patterns on a geology map.

Back 36

non-plunging fold

Front 37

A fold with an inclined axis. The strike of its beds converge and diverge. A series of ______ folds shows a zig-zag outcrop pattern.

Back 37

Plunging fold

Front 38

____ are uplifted sections of earth and ____are downdropped sections of earth that are both bounded by ____ faults.

Back 38

Horts //grabens // normal

Front 39

Divergent plate boundaries yield mostly ___ and are found ____.

Back 39

normal faults // basin range province of US

Front 40

Convergent plate boundaries yield mostly___ and are found ___.

Back 40

reverse and thrust faults // Andes, Himalayas

Front 41

Transform plate boundaries yield mostly ___ and are found ___.

Back 41

strike-slip faults // San Andreas

Front 42

Rock that has behaved in a brittle manner

Back 42

Fractured rock

Front 43

Fractures across which there has been no displacement

Back 43

rock joints