Plate tectonics Flashcards
Focus
spot inside the earth where the rock breaks
Epicenter
Spot on the surface of the earth directly above the focus
Seismic wave
Rock under the earth surface moves or breaks, energy travels in this form
earthquake
the ground to shake and vibrate
Primary (P waves)
move the fastest (compress and expand the material through which they move)
Secondary (S waves)
Move slower (vibrate the rock up and down or side to side) Cant travel through liquid
Rayleigh waves
rolling type of surface ground moves up and down
Love wave
horizontal surface motion is side to side
The most destructive earthquakes are caused by the passage of surface waves, because
they occur at the surface were the ground shakes up and down and side to side
Andrija mohoraovicic discovered (MOHO)
Mantle
Beno Guttenberg refined
Oldhams work by locating the depth of the core-mantle boundary
Mantle has two zone
lower part asthenosphere is solid but behavior is plastic like
lithosphere is upper includes mantle and crust and is cool and rigid.
Mesophere
lower mantle
Inter core is a
solid
outer core is a
liquid
Crust has two distinct regions
oceanic and continental
Isostasy
Meaning standing equal (gravitational and buoyant forces balance one another)
The earth’s crust is thicker beneath a mountain because
mountain sink until the upward buoyant force balances the downward gravitational force
Alfred Wagener (1880-1930)
Proposed that the continent were at one time joined together to from the super continent of Pangaea-“universal land”
Wagner evidence to support his hypothesis
Jigsaw fit of continents fossil evidence Matching rock types Structural similarities in mountain chains on different continents Paleoclimatic evidence
Mapping of the ocean floor revealed
Huge mountain ranges in the middle of the ocean
Deep trenches alongside some continental margins
(Deepest parts of the ocean are near continents, and out in the middle of the ocean it is shallow)
Sea floor spreading (Harry Hess)
Sea floor is not permanent (constantly being renewed)
Mid-ocean ridges are sites of new lithosphere
Oceanic trenches are sites of lithosphere destruction (subduction)
Supports of seafloor spreading
Lava erupted at the mid ocean ridges is rich in iron
Magnetite crystals align themselves to earth’s magnetic field
Magnetic poles file- known as magnetic reversal
Plate tectonics
Lithosphere is divided up into 8 large plates
explains the changing surface features of the Earth
Continents move because they are embedded within the drifting plate
Theory of Plate Tectonics
Plate sections of the Earth are strong, rigid out layer-the lithosphere
Plate consist of uppermost mantle and overlying crust
Plates overlie and ride atop the weaker asthenosphere
Earths plate move in different direction and at different speeds
Oceanic plate tend to move faster
Continental plates tend to move slower
Plate tectonic
8 major plates
plates are in motion and continually changing
Largest plate is the Pacific Plate
Several plate include an entire continent and a large area of seafloor
Interaction between plate occur along
plate boundaries
Creation and destruction of lithosphere occurs
along plate boundaries
Earthquakes, volcanoes, and mountains occurs along
plate boundaries
Divergent Plates magma generation and lithosphere (new) and
Plates move away from one another New crust is formed as lava fill in the gaps between plates Sea floor spreading(mid ocean ridge) On land (rift valley) Shallow earthquakes
Convergent Plate Boundaries Magma generation and lithosphere destruction and
moves toward each other
Oceanic crust (basaltic) is destroyed
Continental crust (granitic) is deformed
Deep earthquakes
Transform Faults Boundaries no magma generation, no formation or destruction of lithosphere and
Plates slide past one another
Join two segments of a mid-ocean ridge
Are oriented perpendicular to mid ocean ridge
(permits plates to move from offset ridge segments)
Shallow but strong earthquakes
Oceanic -oceanic convergent
older and the denser plate descends beneath the other (subduction)
as the plate descends partial melting of mantle rock generates magma and volcanoes
If volcano emerges can form islands
Oceanic-continental convergent
Denser oceanic plate subducts beneath the less dense continental plate
As plate descends, partial melting of subducting rock and generates magma
Mountain produced by the volcanic activity from subduction of oceanic lithosphere and compression from convergence are called continental volcanic arcs
Continental-continental convergent
Continued subduction can bring two continents together
Less dense, buoyant continental lithosphere does not subduct
Collision between two continental blocks
The process products mountains
At plate boundaries
volcano, earthquakes happen 80% of the world earthquakes occur in subduction zones of the ring of fire
Earthquakes
occur on or between plate boundaries
Strain begins at depth as elastic deformation (bending)
Build up of stress exceeds the rocks elastic limits, the rock breaks
This is how faults are forms
Earthquakes are measurement
Richter scale measures the energy released on term of the ground shaking
Each increase of one unit on the scale is a ten-fold increase in amplitude
Tsunami
Giant sea wave or series of sea waves
Reverse faults earthquakes thrust the seafloor upward
Huge displaced mass of water drops back down to sea level and a large wave is generated
Three type of stress caused by interaction between plate boundaries
Compression stress (push plate together) Tensional Stress (slabs pulled apart) Shear stress (slabs are both pulled and pushed_SLIDING)
Rocks responded to stress in 3 different ways
Elastic deformation(returning to original shape Like a rubber band) Brittle deformation (breaking) Plastic deformation(flowing)
Syncline (with)
Layers tilt in toward a fold axis
Anticline (against)
Layers tilt away from axis
Foot wall
below
Hanging wall
above
Reverse fault
Hang wall Goes up the slide (compression, convergent)
Normal Fault
Hang wall drops (think of a slide) Tension, divergent
Strike-slip fault
rock slips past one another with very little vertical displacement-horizontal
More that ___% of Earths water is Ocean
97
Only ___% of Earths water is available to us as water (vapor, ground water, and freshwater)
1
Hydrological Cycle Earths water are constantly circulating the driving forces are
Heat from the sun and force of gravity
Processes involved in the hydro-logic cycle
Evaporation Precipitation Infiltration ( soak up water) Runoff Transpiration(plants release water)
Groundwater occurs in the
saturation zone (water has filled all pore spaces)
Soil moisture is above the
saturation zone in the unsaturated zone
The water table is the boundary between
saturation zone and unsaturated zone
Depth of water table varies with
precipitation and climate (Zero in marshes and swamps and hundreds of meters in some deserts)
Perennial lakes and streams the water table is
above the land surface
Water table tends to rise and fall with the surface of
topography (shape of the land )
Porosity ratio
open space in the soil sediment, or rock to total volume of solid s plus voids- the amount of open space underground
Permeability is the
degree to which ground water CAN FLOW through a porous material(higher permeability, greater potential for fluid flow)
Aquifers are
reservoirs of groundwater
Aquifers generally have high______ and high ______.
porosity, permeability
Perched water table occurs when
discontinuous, low-permeability layers in an unconfined aquifer intercept percolating water above the water table
Land Subsidence
extreme ground water withdrawal by pumping from wells can result in lowering of the land
Caverns and Cave (Ground water has carved out magnificent caves and caverns
Dissolving action of ground water “eats away” at rock mostly limestone
Rain water chemically reacts with CO2 in the air and soil, producing carbonic acid.
Karst regions
are soft rolling hills or sharp, rugged surface (these areas are where sinkholes, caves and caverns define the land surface.
Sinkhole are
funnel shaped cavities in the ground that are open to the sky They form from conditions of drought and the over withdrawal of groundwater
Surface water
streams, lakes, and reservoirs
Infiltration of water is controlled by
Intensity and duration of precipitation Prior wetness condition of the soil Soil type Slope of the land Nature of the vegetative cover
Erosion
Erosive sculpting action carves the lands surface
Deposition
Shapes the land as sediment is deposited
Fast water transports sediment Slow
water deposits sediment
Factors that determine velocity (speed)
Slope-gradient Channel characteristics (size and shape) Discharge-volume of water moving past a given point in a certain amount of time
Stream speed usually not constant along length of a stream. As the stream moves down slope, the gradient ____ and the channel widens. Discharge usually increases as tributaries add water
decrease
Stream erosion
loosely consolidated particles are lifted by abrasion and dissolution
Stronger currents
have higher energy, lifting and transport more and bigger particles, turbulent versus laminar flow
Drainage basin
they land area that contributes water to a stream
Continental divide
Is the divide of the drainage basin
ABRASION
occurs when sediment and particles scour a channel
HYDRAULIC
erodes and moves great quantities of sediment and rock
Laminar flow
can lift and carry only the very smallest and lightest particles
Turbulent flow can
move and carry range of particles sizes Making water murky
V shaped mountains
Fast moving rapids and beautiful waterfalls are characteristic
Water speed varies within a channel …
It is slower along the stream bed and greater near the surface. Maximum flow speed occur mid-channel
Floodplain
Meandering streams create a wide belt of almost flat land
Natural levees
when flooding occurs, sediment is deposited in the flood plain. Large coarse sediment creates natural levees
Delta
is where a flowing stream meets a standing body of water. The flow slows down and the stream dumps sediment
Glaciers are powerful agents of
erosion and deposition. Glaciers plow and scrape and pluck up rock and sediment. Glaciers are like a sled as it carries its heavy load to distant places
Two types of glaciers
Alpine-mountains
Continental- cover a continent Greenland or Antarctica
U shape valley are formed by
Glaciers
till
When glaciers ice melts, it drops a poorly sorted, heterogeneous load of boulders, pebbles, sand, and clay
Accumulation
makes the glacier grow
ablation
as ice melts, sublimates, or breaks off
wind blows everywhere, impact on sculpting the land is minor
Strong winds frequently
vegetation is sparse or absent
surface particles are small
Basel sliding
melting water at the base of the glacier
Seismic waves are classified as body waves and surface waves. An example of a body wave is a
primary waves (P waves)
The fastest seismic wave is a
primary wave P wave
Secondary waves can travel through all areas of the earths except
Outer core (made of liquid)
When earthquakes occurs, energy radiates in all direction form its source. The source is also referred to as the
focus
The founding of the theory of continental drift is credited to
Alfred Wegener
According to the theory of seafloor spreading, molten rock is rising up along
mid ocean ridges
The ocean crust becomes progressively
older away from the mid ocean ridges
Evidence supporting the existence of the Pangaea
Geometrical fit between south America and Africa
Late Paleozoic Glacial features
Similar fossils on different continents
Magnetic surveys of the ocean floor reveal
alternating strips of normal and reversed polarity paralleling the mid-Atlantic ridge
The theory of plate tectonics state that
the lithosphere is broken up into several plates that move as a result of convective motion in the asthenosphere
_______most effectively outline the edges of the lithosphere plates
Lines of earthquakes epicenters
Which type of convergence will result in a volcanic island arc
Oceanic to oceanic
The amount water able to be contained in the subsurface depends on
permeability
A rock’s permeability can be described by its
density
The region above the zone of saturation is called
Zone of aeration
When a perched water table intersects the surface on a hillside, the result is
a spring
A rock that is readily attacked by chemical weathering is
Limestone
If you were to examine the profile of a typical river, you would probably find that the gradient is
Steepest near the head
Which of the following is associated with area of karst topography
Caverns soluble rock and sinkhole
What is infiltration
Water soaking into the ground
The most important agent of erosion is
Water
The typical mountain valley that has been subjected to glaciation is shaped like
U shaped
Glaciers will retreat when the amount of accumulation
Is less than the amount of ablation each year
Point bar typically form
On the inside bend of a curved stream channel
