Tectonics, Earthquakes, & Volcanism Flashcards
What is an eon?
the longest time period in the geologic time scale; we are currently in the Phonerezoic Eon
What is an era?
the longest time period in the eon; we are in the Cenozoic Era
What is a period?
the longest time period in the era; we are currently in the Quaternary Period
What is the difference between absolute and relative time?
- absolute: measured in years
- relative: measured in events
What is stratigraphy?
the study of the formation of rocks over relative time
What is the Principle of Superposition?
the idea that rock layers are younger towards the surface and older below the surface
What is the Principle of Uniformitarianism and why is it significant?
- the same processes we see today have always occurred throughout geologic time
- allows us to make assumptions about how rock formations were created
How do we know about the interior of the Earth?
- information that has been collected via earthquakes
- seismic waves travel through different materials in the interior at different rates
How did the Earth form (3)?
- condensed from a nebula of dust, gas, and icey comets about 4.6 billion years ago
- as they cooled, they solidified and sorted by density
- more dense material was sorted towards the center and less dense material was sorted towards the surface
What is Earth’s energy source (2)?
- interior is hot and heat migrates outward towards the surface
- drives movement of material and volcanic activity
What is the content of Earth’s core (2)?
- inner core: solid, pure iron; above melting point but does not melt due to pressure and weight of overlying material; very dense
- outer core: molten iron
What is the content of Earth’s mantle (4)?
- hot; not as hot as core
- mostly solid
- represent greatest volume of Earth
- consists of lower mantle, upper mantle, and asthenosphere
What is the content of Earth’s lithosphere (2)?
- uppermost mantle: rigid
- mhorovicic (moho) discontinuity: boundary between uppermost mantle and crust; seismic waves
What is the content of Earth’s crust (2)?
- oceanic crust thinner
- continental crust thicker`
What is the Geologic Cycle (3)?
- the rock cycle: the production of different types of rocks
- the tectonic cycle: the movement and deformation of the crust
- the hydrologic cycle: erosion, weathering, and movement of eroded material
What are the elements that combine to make rocks (8)?
- oxygen
- silicon
- aluminum
- iron
- calcium
- sodium
- potassium
- magnesium
What are minerals?
inorganic natural substances with a specific formula and some sort of crystalline structure
What are the seven properties of minerals?
- hardness
- color
- density
- luster
- fracture
- taste/smell
- magnetism
What are rocks?
an assemblage of minerals that are bound together as part of the lithosphere
What are the three types of rock?
- igneous
- sedimentary
- metamorphic
How do igneous rocks form?
form from material that has melted under high pressure/temp. inside the mantle/crust
What is the difference between magma and lava?
- magma: moleten rock below the surface
- lava: molten rock above the surface
What is the difference between intrusive and extrusive igneous rocks?
- intrusive: cooled below the surface at a slower rate; course grain
- extrusive: cooled above the surface at a faster rate; smooth grain
What is a pluton?
intrusive igneous rock formation; mass of slowly cooling rock
What is a batholith?
massive structure comprised of a number of plutons
How much of the Earth’s crust consists of igneous rock?
- 90%
- typically granite for continental crust and basalt for oceanic crust
How do sedimentary rocks form?
form from eroded rock/sediment that is deposited in low-lying areas
What are the three types of sedimentary rock?
- clastic: form from other rock sediments
- organic: form from organic material
- chemical: form from minerals suspended in water
How do metamorphic rocks form?
- experience a change in structure after encountering intense heat/pressure
- tend to be harder and more resistant to erosion/weathering
What is the difference between regional and contact metamorphism?
- regional: occurs when rocks are buried below the surface and subjected to high heat/pressure over a long period of time
- contact: occurs when rocks come into contact with something very hot
What is the difference between foliated and nonfoliated rocks?
- foliated: wavy lines (gneiss, schist)
- nonfoliated rocks: uniform (marble, quartzite)
What is the Theory of Continental Drift (3)?
- developed by Alfred Wagner in 1912?
- explains why continents fit together like a puzzle
- over time the continents drifted apart
What are two pieces of evidence that support Wagner’s theory?
- matching fossil records across continents
- matching rock formations across continents
What is the Theory of Plate Tectonics?
the idea that the Earth’s crust is divided into 14 tectonic plates which float on the asthenosphere
What are the four processes of plate tectonics?
- upwelling of magma: occurs along some plate boundaries
- lithospheric plate movements: upwelling of magma forces lithospheric plates away from one another
- seafloor spreading: creation of new oceanic rock pushes everything outward
- subduction: older crust dips down below another tectonic plate
What are you likely to encounter near subduction zones?
volcanoes and earthquakes
What are the two mechanisms of plate motion?
- ridge push: upwelling of magma at mid-ocean ridge
- slab pull: oceanic crust is pulled below continental crust
What are the three interactions at plate boundaries?
- divergent: occurs at mid-ocean ridge and rift zones
- convergent: two plates converge together and create a subduction zone
- transform: lateral side-to-side movement causes earthquakes but no volcanoes
What are hot spots (4)?
- volcanic activity not found along tectonic plate boundaries
- 50-100 hotspots worldwide
- example: Hawaii and Yellowstone
- can be stationary or appear to move due to plate movement
What is deformation?
how stress affects rock
What are the three types of deformation?
- tension: stretching
- compression
- shear: twisting/lateral movement
What are the impacts of deformation (2)?
- folding: rock is slowly bent
- faulting: rock breaks
What is the difference between ductile and brittle rocks?
- ductile: malleable/bendable
- brittle: more likely to break
What is the difference between an anticline and a syncline?
- anticline: top end of folding curve
- syncline: bottom end of folding curve
What is warping?
- continental crust curves upwards
- forms basins/domes
What are the three types of faults?
- normal: tensional stress; divergent; hanging-wall side moves down, footwall side moves up; results in fault scarp/escarpment
- reverse: compressional stress; convergent; hanging-wall side moves up, footwall side moves down
- strike-slip/transform: shear stress; right lateral vs left lateral
What are earthquakes?
buildup of energy on both sides of fault is released
What is the focus?
location along the fault plain where the earthquake actually originates
What is the epicenter?
where the earthquake occurs at the surface
What is aftershock?
earthquake that occurs after the main earthquake
What is a seismograph?
instrument that records vibrations when earthquake occurs; can pinpoint epicenter and focus
What is the difference between a qualitative and quantitative scale?
- qualitative: based upon the impact of the earthquake
- quantitative: measures the magnitude of energy released by the earthquake
What are the three scales used to measure earthquakes?
- moment magnitude
- modified mercalli
- richter
What are seismic hazard zones?
plate boundaries
What was the magnitude of the Loma Prieta earthquake
6.9
Where does volcanic activity usually occur (3)?
- subduction zones
- mid-ocean rifts
- hot spots
What are the two defining characteristics of volcanic lava?
- high viscosity: thick and slow
- low viscosity: thin and fast
What are the two types of volcanic eruptions?
- effusive: gentle; low viscosity; shield volcanoes; basalt rock
- explosive: violent; high viscosity; composite volcanoes; pyroclastic material
What are the two types of lava?
aa: jagged edges
pahoehoe: thin crust cools; remains melted below
What are cinder cones?
much smaller than volcanoes; no lava; formed under a series of eruptions spewing only pyroclastic material
What is a caldera?
depression which forms when summit of volcano collapses
What are the three types of orogenesis?
- oceanic-continental convergence: more dense oceanic crust dips down below less dense continental crust (Andes Mountains)
- oceanic-oceanic convergence: older sea floor dips down below newer sea floor (Japan, Indonesia, Philippines); creates trenches
- continental-continental convergence: continental plates crumple into each other (Himalyan Mountains); volcanoes don’t usually occur, but earthquakes do
What are fault block mountains (4)?
- pairs of normal faults act together to create a mountainous environment
- horst: upfaulted block
- graben: downfaulted block
- example: Basin & Range, United States
