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