Test 3 Flashcards
Scarification
Human induced mass movements.
Geologic time scale
- Relative dating
2. Absolute dating
Relative dating
Determining the order of what occurred first. Uses the “Principle of superposition” as well as fossils.
Principle of superposition
Younger rocks are superimposed on top of older rocks.
Absolute dating
Determining the specific number of years before the present. Uses “radiometric dating.”
Radiometric dating
Measuring time by the know decay rate of certain elemental isotopes.
Catastrophism
Emphasizes the concept that rapid, large-scale catastrophic events have shaped the planet.
Uniformitarianism
Assumes the same physical processes that are occurring today have operated throughout geologic time.
Punctuated Equilibrium
Episodic catastrophic interruptions in the otherwise generally uniform processes conceptualized by Stephan Jay Gould.
How old is Earth?
4.6 billion years old.
How did Earth’s structure form?
Gravity brought heavy elements to center, formed layers.
What processes make Earth emanate heat from the center?
Conduction and convection.
Characteristics of the core
- 1/3 mass, 1/6 volume.
- Solid iron inner core, molten less dense outer core.
- Generates magnetic field.
Characteristics of the mantle
- 80% of Earth’s volume.
- Increasing temperature with depth.
- Increasing stiffness with depth.
Characteristics of the asthenosphere
- Plastic layer below lithosphere.
2. Movement in this layer produces tectonic activity.
Characteristics of the lithosphere
- Rigid outer layer of rock.
2. Includes continental and oceanic crust.
Continental Crust
Less dense (granitic) Silica, aluminum, potassium.
Oceanic Crust
More dense (basaltic) Silica, magnesium, iron.
Isostasy
Isostasy controls the regional elevations of continents and ocean floors in accordance with the densities of their underlying rocks.
Isostasy adjustment
Ocean basins have gotten larger since the end of the last glacial cycle because ice sheets that once covered North American and Europe have melted in the last 20,000 years.
What are the most abundant elements in the crust?
Oxygen and silicon.
Definition of rock
Rock is a chunk of Earth’s surface, usually lots of minerals together.
Mineral
Inorganic, natural compound with a specific chemical formula and possessing a crystalline structure.
4 Mineral Families
- Silicates
- Oxides
- Sulfides & Sulfates
- Carbonates
Silicates
Silicon and oxygen
Oxides
Oxygen and metallic elements
Sulfides & Sulfates
Sulfur and metallic elements
Carbonates
Carbon with oxygen and other elements
3 types of rocks
- Igneous- liquid rock that cools.
- Sedimentary- forms from pieces of other rocks or through a chemical process; evaporation.
- Metamorphic- changed though heat pressure and chemical fluids, heat up not hot enough to melt.
How to classify Igneous rocks
Igneous rocks are classified by color (light [felsic]/dark [mafic] and the size of crystals large [intrusive]/small [extrusive].
Lithification
The process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock.
Plate tectonics
Plates shift and move over the Mantel.
Mid-ocean ridges
Underwater mountain range, formed by plate tectonics. This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.
3 plate boundaries
- Divergent
- Convergent
- Transform
Divergent boundary
Found in deep oceans. Two plates pulling apart from each other. Mid-ocean ridges.
Convergent boundary
Collision of two plates. The more dense oceanic plate goes under the less dense continental plate usually. Causes earthquakes and volcanoes. The Himalayas are a result of this.
Transformation boundary
Two plates slide by one another in opposite directions. The San Andreas Fault.
What is the correlation between earthquakes/volcanoes and plate boundaries?
Convergent boundaries cause them when the oceanic plate subducts the continental plate and starts to melt.
Hot spots
Volcanic regions thought to be fed by underlying mantle that is abnormally hot and therefore rises. Hawaii was formed this way.
Relief
Vertical elevation difference in the landscape.
Topography
The undulating form of the Earth’s surface, including its relief.
Origin of the Continental Crust
- Inactive remnants of tectonic activity.
- Folding and faulting from crustal movement.
- Volcanic features.
Craton
Older nucleus built on to form continents.
Continental Shields
Where craton appears at the surface.
Terranes
Pieces that become attached to plates.
3 types of Stresses
- Tension (stretching)
- Compression (shortening)
- Shear (twisting and tearing)
2 types of strain (how rocks respond to stress)
- Folding (bending)
2. Faulting (breaking)
Folding (bending)
Anticline and syncline. The landscape is all wavy and shit.
Faulting (breaking)
- Normal fault
- Reverse fault
- Strike-slip fault
Normal Fault
Pulling apart. Tensional stress.
______
______/–>
<–/
Reverse Fault
Pushing together. Compressional stress.
______
//
Strike-slip Fault
Sliding besides each other. Right lateral and left lateral. The one below is left-lateral because while standing on one side and facing the other, it shifted to the left.