Lecture 4 Flashcards
Tectonic plates
Large subdivisions in the crust of the planet, which are generally in motion over long geological time scales
Plate tectonics
The study of movement of tectonic plates
Fault
Major fracture in the continuity of two regions of rocks
Oceanic crust
One of the two major divisions in types of tectonic plates:
-Mainly found under oceans
-Relatively young in geological timescale
Continental crust
The other major division in types of tectonic plates:
-Varying ages but relatively older than oceanic crusts
-Generally found out of water
Asthenosphere
Denser, weaker layer below the lithosphere
Temperatures are hot enough that rock behaves like a liquid (temps increase towards the core)
Lithosphere
The solid, outer part of Earth
Convection current
Moves tectonic plates
- current that flows up from the core of the Earth and circulate under the asthenosphere
Ridges
1st process that convection currents move tectonic plates through: creation of new plate at ridges (push)
-pushes existing plate away from the ridge
Subduction zones
2nd process that convection currents move tectonic plates through: destruction of plates at subduction zones (pull)
Push-pull
Process driving plate tectonics
Divergent boundary
Occurs when 2 tectonic plates move away from each other
Magnetic pole reversals
The locations of magnetic north and south generated by Earth’s magnetic field switch over time
Convergent boundary
When 2 plates come together
Transform boundary
Places where plates slide sideways past each other
Sea floor spreading
The process of tectonic plates moving apart at divergent boundaries
Hydrothermal sea vent
Weak point in the sea floor where water and minerals heated geothermally enter the ocean
-commonly found along divergent boundaries
-may have played an important role in the evolution of life
Rift valley
A divergent boundary which forms on land
Oceanic trench
Formed when oceanic crust meets continental crust at a divergent boundary
(steep depressions in the deepest parts of the ocean)
Transform faults
When two plates slide past each other, results in large characteristic faults
Elastic rebound theory
Earthquakes occur because plates at transform boundaries cannot move continuously and energy builds up at the transform fault, until energy stored is released all at once in a sudden movement of the 2 plates
Angle of insolation
Angle at which sunlight hits the planet (differs across the planet)
Albedo
Reflectivity of a surface
Igneous
Type of rock found in crust: formed from the cooling of molten rock from the mantle
Sedimentary
Type of rock found in crust: formed from the pieces of other rocks and sometimes organic material
Metamorphic
Type of rock found in the crust: minerals that have been changed from their original form through intense heat and pressure
Landform
Natural feature of the physical landscape of the Earth
Weathering
Disintegration (weakening) and decomposition (break down) of rock
3 types: physical, chemical and biological
Physical weathering
Mechanical break-up of rock
Occurs in the presence and absence of terrestrial life
Caused by water, ice, physical contact between 2 sets of rocks
Chemical weathering
Mineral breakdown caused by chemical reaction
Also occurred before terrestrial life
Biological weathering
Only occurred on land once life became terrestrial
Can seem mechanical (tree roots breaking up rock)
Can also seem chemical (lichen using acids to break down rock)
Difference from other forms of weathering: must have a biological component
Erosion
Material which has been weakened or broken down through weathering is moved from its original location
The rock cycle
The conversion of one rock type to another is continuous
