Geomorphology Final Exam Study Guide Geologic Structures STRUCTURAL GEOLOGY – concerned with shapes, arrangement, interrelationships of bedrock units & endogenic (within) forces that cause them. Tectonic Forces Stress & Strain + Compressed Stress – shortening strain + Tensional Stress – stretching or extensional strain + Shear Stress – shear strain Behavior of Rocks + Elastic – rock returns to original shape after increased / decreased stress. - Elastic Limit – point when rock reaches too much stress (Brittle / Plastic Fracture) + Plastic – hot under pressure + Brittle – rock reaches too much stress quickly and cracks. FACTORS: dependant on rock lithology, amount of time, and pressure. Strike – intersection of a horizontal unit against an Inclined plane. (THAT LINE) Dip- angle horizontal to the rock layer that’s inclined (ALWAYS MAX. ANGLE)
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Geomorphology Final Exam Study Guide · Geomorphology Final Exam Study Guide Geologic Structures STRUCTURAL GEOLOGY – concerned with shapes, arrangement, interrelationships of bedrock
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Geomorphology Final Exam Study Guide
Geologic Structures
STRUCTURAL GEOLOGY – concerned with shapes, arrangement, interrelationships of bedrock
units & endogenic (within) forces that cause them.
Tectonic Forces
Stress & Strain
+ Compressed Stress – shortening strain
+ Tensional Stress – stretching or extensional strain
+ Shear Stress – shear strain
Behavior of Rocks
+ Elastic – rock returns to original shape after increased / decreased stress.
- Elastic Limit – point when rock reaches too much stress
(Brittle / Plastic Fracture)
+ Plastic – hot under pressure
+ Brittle – rock reaches too much stress quickly and cracks.
FACTORS: dependant on rock lithology, amount of time, and pressure.
Strike – intersection of a horizontal unit against an
Inclined plane. (THAT LINE)
Dip- angle horizontal to the rock layer that’s inclined
Plunging Fold – folds that are not horizontal anymore, ‘U’ shaped ridge.
Folds are formed from COMPRESSIONAL SHORTENING
DUCTILE (Plastic Deformation)
Open Folds Isoclinal (hairpin) Folds
Overturned Folds Recumbent Folds
Plunging Folds (noses)
Unconformities
Angular – sedimentary beds of differing dip on either side of the unconformity.
Disconformity – sedimentary beds of the same orientation on either side of the
unconformity.
Nonconformity – sedimentary beds overlying unconformity developed on
crystalline rocks. (Igneous / metamorphic)
Joints & Faults
STRESS
- Tensional (pull apart) -rifting, flexure
-orientation ‘perpendicular’ to stress
- Shear
-orientation 30o-45o from the max / min stress axes
TOPOGRAPHIC EXPRESSION
- Physical properties of the rock and accelerated weathering and erosion
rates.
Fins – when joints become dominate,
cap rocks preserve the below sediments.
Faults Dip-Slip
Normal Faults
Reverse (thrust) Faults – up and over the top.
Strike-Slip
Left or Right lateral (San Andreas Fault)
Oblique-Slip (scissors)
Components of both the Dip-Slip & Strike Slip.
• Fault scarp
– steep linear bluff – Relief formed solely by movement • Fault-line scarp – Relief caused by differential erosion along fault • Composite scarp – Combination of the 2 above • Mountain landforms
– Horst – Graben • Forms basin & range
Within the Basin and Range Province, the Earth’s crust has been stretched up to 100% of its original width. The entire region has been subjected to extension that Thinned and cracked the crust as it was pulled apart.
Volcanism Lava – magma at the earth’s surface, silica content controls “explosiveness”. Pyroclasts – fragments of rock due to the explosiveness of
The volcano classified to size & shape.
Lava Flow
Extrusive Rocks – (Plugs & Domes)
Volcanoes
Extrusive Rocks & Gases
-Scientific study of Volcanism
-Gases
-Primarily H20
-CO2, SO2, H2S, HCI
-Gases & Pyroclasts
-Ashfall
-Pyroclastic Flow
Magma
Physical properties dependent on;
-Temperature (700o – 1300o C or above)
-Composition - felsic (silicic) to mafic
-Gas Content – several % by weight (H2O, CO2, SO2, ect.)