Exam 3 Flashcards
(26 cards)
Describe the geologic time scale
- Timeline of earth history
- Earth is 4.6 billion years old
Describe geologic time
- Absolute time is the actual # of years before present
- Relative time is the sequence of events
- Principle of superposition is youngest beds of rock superposed toward the top of a formation and the oldest at the base if they have not been disturbed
- Principle of uniformitarianism is the same geologic processes happening today that have happened in the past
How was earth formed?
Condensed from a nebula of dust, gas, and icy comets
Describe earth’s core
- Dense and metallic
- Solid iron in the inner core, molten iron in the outer core
- Rotation of Earth affects fluid outer core and generates Earth’s magnetic field
Describe earth’s lithosphere and crust
– “Floats” on the Asthenosphere and is broken into plates
– The Moho is a rocky shell of continents and ocean floor that separates crust from the mantle
What are the 3 sub cycles in the geologic cycle?
- The hydrologic cycle is the chemical and physical action of water, ice, and wind
- The rock cycle produces igneous, metamorphic, and sedimentary rocks
- The tectonic cycle brings heat energy and new material to the surface and recycles old material
Define mineral
An inorganic natural substance with a chemical formula and usually a crystalline structure
Define rock
An assemblage of materials including minerals and organic matter
Describe the igneous process
- Magma intrudes into crustal rocks to form intrusive rocks
- Magma extrudes as lava onto the surface to form extrusive rocks
- Slow cooling intrusive igneous rock forms a pluton and multiple plutons form a batholith
- Igneous rocks make up 90% of Earth’s crust
Describe the sedimentary process
Most form when eroding fragments of existing rock or organic materials are transported downslope by water, ice, wind, and gravity
-Clastic, organic, and chemical sedimentary rocks
What are clastic sedimentary rocks?
Rock fragments that compact under the weight of overlying layers and then cement and harden
What are organic sedimentary rocks?
From shells and skeletons of marine organisms and the decayed remnants of plants
What are chemical sedimentary rocks?
In marine and saline inland seas, some minerals separate from water to form solid sedimentary deposits
Describe the metamorphic process
- Any igneous or sedimentary rock can become metamorphic through intense heat and pressure that alter chemical and physical properties
- Harder and more resistant to weathering
- Regional metamorphism and contact metamorphism
What is regional metamorphism?
Rocks buried inside crust subjected to high temperatures and pressures over millions of years
What is contact metamorphism?
Magma rising to the surface “cooks” nearby rocks
What are the textures of rocks?
- Foliated rocks have thin wavy lines
- Nonfoliated rocks have a crystalline structure
What are the four processes of plate tectonics?
Seafloor spreading, subduction, upwelling of magma, and lithospheric plate movements
What is seafloor spreading?
- It builds mid- ocean ridges and drives continental movement
- Mid-ocean ridges are spreading centers
What are subduction zones?
- Deep-ocean trenches where lithosphere sinks
- When denser oceanic crust hits lighter continental crust, it slides beneath, forming a subduction zone
What two mechanisms drive plate motion?
- Ridge push (mid-ocean ridge pushes the plates away from the ridge)
- Slab pull (near the trench, gravity pulls plate downward)
What are the three types of interactions at plate boundaries?
- Divergent (plates pull apart)
- Convergent (plates collide and produce shaking and volcanoes)
- Transform (plates slide past one another)
What are hot spots?
Upwelling magma to the surface not associated with plate boundaries
What is deformation?
Stress affects rock through deformation
-The types of stress are tension (stretches), compression (shortens), and shear (twists or tears)
