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Lab 3 – Structural Geology and Earthquakes

Lab 3 – Structural Geology and Earthquakes. Definitions. Structural Geology – study of how geologic units (bodies of rock or sediment) are arranged when first formed and how they are deformed afterward. Geologic Map. Geologic map – shows the distribution of rocks at the Earth’s surface.

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Lab 3 – Structural Geology and Earthquakes

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  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

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