1. Lab 3 – Structural Geology and Earthquakes

2. Definitions
Structural Geology – study of how geologic units (bodies of rock or sediment) are arranged when first formed and how they are deformed afterward.

3. Geologic Map
Geologic map – shows the distribution of rocks at the Earth’s surface.
Formations – mappable rock units
Beds – subdivisions of formations
Example: Cretaceous Kootenai = sandstone formation, Gastropod Limestone = bed within Kootenai
Contacts – boundaries between geologic units

4. Geologic Cross Section
Geologic cross section – a drawing of a vertical slice through the Earth.

5. Geologic Block Diagram
Block diagram – a combinations of the geologic map and cross section.

6. Strike and Dip Attitude – the orientation of a rock unit or surface.
Strike – the compass bearing (direction) of a line formed by the intersection of a horizontal plane and an inclined layer (bed/stratum) of rock, fault, or fracture.
Dip – the angle between a horizontal plane and the inclined (tilted) stratum, fault, or fracture.
Dip direction – perpendicular to the line of strike, direction in which water will run downhill.
Dip angle – inclination of dip down from the horizontal line.

7. Unconformities
Disconformity – an unconformity between parallel strata.
Angular unconformity – an unconformity between nonparallel strata.
Nonconformity – an unconformity between sedimentary rock/sediment and non-sedimentary (ign./met.) rock.

8. Faults
Types: normal, reverse (high angle), thrust (low angle), transverse (strike-slip)
Remember:
Stress fields
Angles
Hanging wall
Foot wall

9. Folds - Antiforms Antiform – “upfold” or “convex folds”
Anticlines - Oldest rocks in the middle
young
old
young

10. Folds – Synforms Synform – “downfolds” or “concave fold”
Syncline – youngest rocks in the middle
old
young
old

11. Other types of folds
Basins
Domes

12. Earthquakes
Earthquakes – shaking motions and vibration caused by release of energy in the Earth.
Epicenter – point on Earth surface directly above the focus (origin of earthquake)
Seismic waves – elastic waves of vibration and shaking cause by stain.
P-waves – primary waves, compressional
S-waves – secondary waves, shear
Rayleigh/Love waves –move along Earth’s surface
Seismograph – instrument to record seismic waves
Seismogram – record of seismic waves

13. Earthquake Damage Damage related to:
Energy
Amplitude
Soil strength
Building strength
Unconsolidated sediment amplifies waves.

14. Earthquake location