Dynamic Earth Test Flashcards
*Our understanding of the earth’s interior is based entirely on the study of ______ _______. Be sure to understand and know how to use page 10 of the ESRTs, the inferred properties of the earth’s interior.
earthquake waves
understand
what did the idea of continental drift suggest?
Suggested that the continents have been moving across the earth’s surface for millions of years.
- Suggested that continents were once together in a super-
continent called Pangaea about 250 million years ago
Evidence for continental drift
✴ The apparent fit of the continents
✴ Fossil correlation
✴ Rock/Mountain correlation
✴ Paleoclimate data (coal in
Antarctica, Glaciers in the tropics)
Wegener’s theory was _______ because he failed to explain
what _______ was driving the ______.
rejected
force
motion
Plate tectonics is a
Theory developed in the mid-1900’s that explained all geologic observations including mountains, earth-quakes, volcanoes, and trenches
How do plate tectonics move?
The lithosphere of the earth is broken up into plates which “float”
on the plastic asthenosphere below
Convection currents in the asthenosphere move the plates around
Plates interact with each other in three ways:
✴ Move towards each other (CONVERGENT)
✴ Move away from each other (DIVERGENT)
✴ Slide past one another (TRANSFORM)
Subduction zone (_________ crust and ________ crust)
continental, oceanic
Oceanic crust is forced down because it’s more dense
Volcanoes, mountains, earthquakes and trenches are common
Example: Western South America
Collision zone (________ crust and ________ crust)
continental, continental
Both plates have the same density and therefore crumple up as they collide
Mountains and earthquakes are common
Example: Himalayas
TRANSFORM PLATE BOUNDARIES
Two plates slide laterally past one another
Earthquakes are common as friction and pressure builds up
Example: San Andreas Fault
Island Arc (_______ crust and _______ crust)
oceanic, oceanic
Two oceanic plates collide and one usually subduct under the other
Volcanic islands, earthquakes and trenches are common
Example: Aleutian Islands
DIVERGENT PLATE BOUNDARIES
Two plates move away from one another
Magma rises at the boundary forming a ridge with a valley and new sea-floor
Alternating bands of magnetic polarity are locked in the sea-floor
Sea-floor rock gets increasing older as you move away from the boundary
Example: Mid-Atlantic Ridge
*HOT SPOTS
There are locations on earth, away from plate boundaries, where volcanic activity occurs
Magma rises from the mantle and forces its way through the lithosphere, forming a chain of volcanoes.
Example: Hawaii
DEFORMATION
When plates interact, rocks are exposed to intense pressure which cause deformation
Rock layers are always laid down _______; if they are observed in any other position, you can infer that
_______ has taken place
horizontally, deformation
The discovery of marine fossils high in mountains is evidence for _____ _____
crustal uplift
Major types of deformation include ________, ________, and ________
folds, faults, tilts
P-Waves
P-Waves
* Move fast
* Can travel through liquid and solid
* Push-pull motion
S-Waves
S-Wave
* Move slow
* Can only travel through solids
* Shear wave motion
The focus is -
The spot within the Earth where an earthquake begins.
Epicenter-
The spot on the surface of the Earth closest to the focus.
Fault-
Crack along which movement takes place.
Graphing foci depth can reveal the type of _____ _________.
plate boundary
Foci will get _______ as you travel along a _________ _____
deeper, subducting plate
Shadow Zone-
An area on the opposite side of the Earth from where an earthquake happens that receives no earth-
quake waves because of refraction of P-waves and absorption of S-Waves into the liquid outer core.
Finding Epicenter Distance
- Determine the difference in arrival time between the P and S waves
- Line a piece of scrap paper along the vertical axis of the reference table
and mark of the location of zero and the difference in arrival time - Slide the paper along the curve until the marks match up perfectly with
the P and S curves - Follow the paper down to the horizontal axis and read the epicenter distance (it is in thousands!)
Finding Travel Time
- Find the epicenter distance for the station using the horizontal axis of the
reference table - Go up to the P or S curve (depending on what you are looking for)
- When you hit the curve, go to the left and read the time off the vertical
axis
Locating the Epicenter Location
- Determine the epicenter distance for three different seismograph location (seismic stations)
- On a map, draw a circle with a radius of the epicenter distance around each seismic station
- At the location where the three circles intersect is where the epicenter of the earthquake was located
REMEMBER: TO FIND THE LOCATION OF THE EPICENTER, WE MUST HAVE DATA FROM ______ DIFFERENT SEISMIC STATIONS
THREE
Don’t forget to study the reference tables!!!
The Richter scale is used to determine what?
How powerful a quake is. It is used to determine an earthquakes strength. It uses numbers to measure the severity of an earthquake.
