GEO LAB Final Part B

Dip

*Angle* between horizontal plane and the inclined layer

Strike

*Direction of a line* formed by the intersection of a horizontal plane and an inclined layer

What are the three types of map scales?

-Bar Scale -Fractional Scale -Verbal Scale

Faults and causes

-Breaks along which movement has occurred -Causes: Tension, compression, shear

Reverse fault

-Caused by compression (which causes shortening) -*Thrust fault* -> very low angle reverse fault -Handing wall moves *upward* relative to footwall

Strike slip fault (lateral faults)

-Caused by shear -Horizontal motion

Normal Fault

-Caused by tension (tension causes lengthening) -Handing wall moves *down* relative to footwall -Caused by gravity

Basin

-Circular structure formed when strata warped downward -Bowl -Youngest at the center

Dome

-Circular structure formed when strata warped upward -Upside down bowl -Oldest at the center

What are the three motions of a fault?

-Reverse slip -Normal slip -Strike slip

Angular conformity

-Unconformity between *nonparallel* strata

Nonconformity

-Unconformity between *sedimentary rock* and *non*-sedimentary rock

Disconformity

-Unconformity between relatively *parallel* strata -Could be caused by a time gap, erosion, etc.

What are the two fold types?

1. Anticline 2. Syncline

What are the two main types of seismic waves?

1. Body waves 2. Surface waves

What are three things that represent a geologic map?

1. Colors 2. Lines 3. Special Symbols

What do the symbols define?

1. Fold axis 2. Fault planes 3. Dipping beds (tilted layers)

What are three common geologic structures?

1. Folds 2. Faults 3. Unconformities

What are the two types of faults?

1. Hanging wall 2. Foot wall

What are the three parts of a fold?

1. Hinge 2. Limbs 3. Core

What three things do colors tell us on a geologic map?

1. It helps us read the map 2. The colors represent a particular rock unit 3. The colors are arranged in a stratigraphic column in which rock units are arranged in boxes from oldest to youngest (bottom to top)

What are the four rules to drawing a contour line?

1. It separates all points of higher elevation from the lower elevation. The distance between two adjacent lines represents a vertical distance called contour interval. 2. Every fifth line is index, and in bold. 3. The horizontal spacing determines the steepness of the land. 4. Lines never cross.

What are five things that the geology of an area has effects on?

1. Landslides 2. Availability of groundwater in wells 3. Amount of shaking from EQ's 4. Presence of available minerals 5. Landscape shaped to a particular kind of plant growth

What are the four components of a topographic map?

1. Map Scale 2. Map Colors 3. Map Symbols 4. Map Location (North arrow)

What three things tell us that rocks are deformed?

1. Original Horizontality 2. Geologic age 3. Understanding changes that take place to rock fabrics during deformation

What are the two types of body waves?

1. P-Waves (compressional) 2. S-Waves (shear)

What is the order of arrival in the seismic waves?

1. P-wave 2. S-wave 3. Surface waves

What are the two types of surface waves?

1. Rayleigh waves 2. Love waves

How do we structurally define rocks?

1. Relative position (dip and strike) 2. Upright vs. overturned

Inclination of surfaces in rocks includes:

1. Rock layers in a fold limb 2. Fault surfaces 3. Rock layers beneath angular unconformity

What are the two deposition principles?

1. Sediments are deposited as layers. 2. A younger layer of sediment is deposited on top of an older layer.

What are three components of unconformities?

1. Stress 2. Erosion 3. Lack of deposition

What two different things measure earthquakes?

1. The magnitude 2. The intensity (damage)

What are the two fold sizes?

1. Wavelength 2. Amplitude

What are the four steps to understanding the geologic problems of a region?

1. What is the geologic history 2. What are the geologic sources 3. Where and how are they formed 4. Do they constitute natural hazards

Geologic Map

A 2-D representation of geology on the earth's surface.

Topographic Map

A 2-D representation of the three dimensional surface of the earth.

Overturned Fold

A fold in which the axial plane is tilted and beds may dip in the same direction on both sides of the axial planes.

Overturned fold

A fold tilted so that one limb is upside down

Recumbent Fold

A fold with a horizontal axial plane.

Symmetrical Fold

A fold with sides showing a mirror image with respect to axial plane.

Asymmetrical Fold

A fold without a mirror image in respect to axial plane.

Earthquake

A natural phenomenon that results from sudden release of energy that radiates seismic waves.

What is a geologic unit?

A volume of a certain rock type of a given range.

Dip direction

Always perpendicular to the line of a strike

Plunge

Angle between fold axis and horizontal

Folded Structures (Two types)

Antiforms (up-folds) --> anticlines Synforms (downfolds) --> synclines

Geologic Structure

Any feature produced by deformation of a rock.

Contacts

Boundaries between geologic units

How do plates deform?

By folding rocks and displacing rocks along faults.

Trend of the plunge

Compass direction measure in the direction that axis inclined downward

Where do body waves travel?

Deep inside the earth.

Fault

Develops as a result of rocks breaking when stressed, rather than bending.

What is it called when in a strike slip fault, the opposite wall moves right?

Dextral.

Cross section

Drawing of a vertical slice through Earth

Seismograph

EQ's generate seismic waves which can be detected using a sensitive instrument called a seismograph.

How do earthquakes occur?

Either naturally or as a result of human activity.

Fold axis

Imaginary stratum Folds bend around this imaginary stratum AKA: hinge line Fold axis lies within the axial plane

Dip angle

Inclination of the water line down from the horizontal plane

Beds

Individual layers of rocks/sediment

What is the dip direction in bedding?

It goes from the older rocks to the younger rocks.

Contour Lines

Lines drawn on a map connecting points of equal elevation.

What fault has the younger rocks in the hanging wall?

Normal-slip faults.

Anticlines

Oldest rocks are in middle 'A' shaped

Angular Unconformity

Pre existing rocks are uplifted and tilted by stress. Then the new sediments deposit horizontally in layers.

What fault has the older rocks in the hanging wall?

Reverse-slip faults.

How do you find the difference in arrival time?

S-P

Disconformity

Sediment supply is cut off, stopping deposition. There is a gap in the sediment record. Then, new sediment layers are parallel to old layers. The surface between the two groups of layers is the disconformity.

Limbs

Sides of the fold

What is it called when in a strike slip fault, the opposite wall moves left?

Sinistral.

Block diagram

Solid block, geo map on top and cross section on sides 3D model of a portion of crust

What causes rocks to move?

Stress.

Map Datum

The MSL or USGS quad.

What does a capital letter on a geologic map represent?

The age of the unit.

Relief

The difference in elevation in a specified area

Dip Direction (Strike)

The direction of maximum inclination for a surface measured with respect to true north-in which all points on that line are of equal elevation.

P-Waves

The first waves to appear on the record and are the fastest moving waves. They travel parallel.

Anticline

The folds with the oldest rocks in their cores.

Syncline

The folds with the youngest rocks in their cores.

What happens in a normal slip fault?

The hanging wall moves down the fault surface and vertically omits rocks layers.

What happens in a reverse slip fault?

The hanging wall moves up the fault surface, and vertically repeats rock layers.

Non Conformity

The interface between igneous rocks are eroded and sedimentary rocks are deposited on top.

Inclined Rock Layer

The layers crop out in V's across valleys. Layers that are inclined in a direction that is a down valley, has a "v" down valley. 0-90 degrees.

Epicenter

The location on the surface directly above the focus.

Dip Amount (Dip)

The magnitude of maximum inclination for a surface measured with respect to teh horizontal plane to the top of bed or fault. Does not exceed 90 degrees.

Focus

The point from which the EQ's seismic waves originate. Also known as a hypocenter.

Seismogram

The record of ground shaking recorded by the seismograph is called a seismogram.

S-Waves

The second waves to appear and are slower than P-Waves. They travel perpendicular to the motion.

Seismology

The study of EQ's and seismic waves that move through and around the earth.

Elevation

The vertical distance from the datum

Why are contour lines important?

They allow us to show the shape of the land surface on a map.

Love Waves

They are much like S-Waves. Their amplitude decreases with depth and does not reach the core or mantle. They have side to side motion.

Rayleigh Waves

They are much like ocean waves. The passage is elliptical. They travel on the surface of the earth and causes major damage.

Vertical Rock Layer

They crop out across the topography. They run straight across all kinds of topography without deviation. 90 degrees.

What do symbols do for us on a geologic map?

They depict the orientation of bedding or layering.

Monoclines

Two axial planes that separate two nearly *horizontal limbs* from a single, steeply inclined limb

Geologic Maps

Two-dimensional map that records the outcrop data using different color & symbols

Horizontal Rock Layer

When it is cut irregularly due to erosion, it exposes the lower layers. The contacts follow the contour lines. 0 degrees (no dip)

Fold

Wraps in rocks layers and occur bended upwards, downwards or sideways.

Synclines

Youngest rocks are in middle 'U' shaped