EARTHSCI 2 Flashcards
rocks are also under stress caused by
forces within the earth
these forces ______________ the rocks on the earth’s crust
push and pull
rocks slowly change their _______
shape and volume
what direction do these rocks go to
up, down, and sideways
these movements of the rocks cause rocks to
break, tilt, fold, or undergo deformation
what are the 3 different types of stress
compression, tension, and shearing
explain compression
squeezes rocks in the crust. causes them to move closer and become denser and smaller in volume. some rocks move up while others move down.
explain tension
pulls on the rocks causing them to stretch over a larger area. becomes thinner in the middle and thicker at the ends.
If the volume increases, density
decreases
explain shearing
pushes the rocks in the crust to opposite directions causing them to twist or tear apart. bends or breaks the rocks apart.
can the 3 types of stress change the volume and form of rocks?
yes
stress can cause the rocks to __________________
fracture or crack
if the rock fractures have not moved, the cracks are called
joints
joints are cracks that are (parallel/ perpendicular) to one other
parallel
the rocks that form joints in more than one direction turn into
blocks
forms where the different sets of joints cross one another
blocks
breaking of rocks along a crack or fracture where rocks can no longer withstand stress
faulting
when is a fault created
when the rocks move along a break or crack
3 types of faults
normal, reversal, and strike-strip
what is a normal fault
one side of the fault that is lower relative to the other side
what do normal faults form
mountains and valleys
mountains that are formed by blocks of rocks uplifted by normal faults are called
fault-block mountains
what is a reverse fault
rocky block that is pushed up relative to the rock on its side
what is a strike-slip fault
adjacent blocks of rocks move sideways and not up and down
an effect on compressional stress
folding
some rocks either break or
bend or crumple
a bend in a rock is called a
fold
what direction can a rock fold
upwards or downwards
what is an upward fold called
anticline
what is a downward fold called
syncline
large folds form mountains which are called
folded mountains
how do scientists gather information about earth’s interior
seismic waves
waves that travel through rocks in all directions
seismic waves
in which part to seismic waves travel
where the ground breaks during an earthquake
how are the earths layers divided
by chemical composition
4 layers of the earth
crust, mantle, outer core, inner core
why do the seismic waves change behavior when it travels from layer to layer
due to the varying densities
2 waves under seismic waves
body waves and surface waves
which type of wave has higher frequency
body waves
why do body waves have higher frequency
they arrive before the surface waves that earthquakes emit
2 types of body waves
p-waves and s-waves
which wave arrives first, p or s
p waves
how were the first waves detected
by seismometers
as p waves travel down the
liquid core
what happens when the p waves travel down to the liquid core
they slow down and bend
where can s waves travel
only through solids
what directions can surface waves go
up, down, rolling motion, and side-to-side-vibration
outermost and thinnest layer of the earth
crust
what is the crust made out of
soil and water; light and rich with silicon
two types of crust
continental and oceanic
difference between continental and oceanic
continental is thicker and has low density rocks while oceanic is thinner and has high-density rocks
lies beneath the crust; extends from the base of the crust to the core-mantle boundary
mantle
two layers of mantle
upper and lower mantle
define the upper mantle
mostly solid, but its more flexible regions contribute to tectonic activities.
rock samples from the upper mantle are brought to the surface by
volcanic activity
what are the rock samples made out of
silicate base rocks that are rich in magnesium
upper mantle mainly consists of a rock called
peridotite
define lithosphere
uppermost layer of the mantle id firmly attached to the crust; rigid, brittle, single structure
define asthenosphere
less rigid, warmer region of the upper mantle
what is underneath the asthenosphere
lower mantle
define the lower mantle
more compact structure; hotter, denser, and more stiff due to intense pressure
extends from core-mantle boundary to the center of the earth
core
what is the core made out of
nickel-iron alloys; fluid outer core and solid inner core
what are the characteristics of tectonic plates
- one plate can carry both oceanic and continental crusts
- a plate float over on the asthenosphere an slides horizontally over it.
- Tectonic plates move at a very slow rate
the movement of tectonic plates is made possible by
heat from the upper mantle
which theory states that the continents are constantly moving
continental drift theory
who made the continental drift theory
alfred wegner
what was the large continent the earth was once made of called
pangaea
what are the concrete pieces of evidence found later on:
- close match between coastlines on opposite sides of the Atlantic Ocean.
- similar rock layers and mountain ranges
- mountain ranges of the same age, structure, and rock type
- fossils of extinct plants and animals
- glacial evidence like scrubs and scratches
- coral reefs and coal-forming swamps found in tropical regions
explain sea-floor spreading
magma intrusion pushes the seafloor away from ocean ridges in both directions as evident in changes in the magnetic stripes found on rocks on the ocean floor
what causes magma to rise
convection currents
hot mantle: rises cold mantle:
sinks
how is a rift formed
magma exerts tremendous force to the lithosphere, causing it to break
who made the seafloor spreading theory
harry hess and robert diez
_______ are places on earth covered with salt water
ocean basins
how are ocean basins formed?
seafloor spreading from volcanic rocks released from the fissures along the mid-ocean ridges
what are the stages of development in ocean basins
embryonic
juvenile
mature
declining
termina
continental collision
explain embryonic
continents start to separate (rift valleys are formed)
explain juvenile
seafloor basalts begin forming. rift valleys are flooded by seawater. mid-ocean ridge is formed.
explain mature
broad ocean basins widen, trenches develop, and subduction begins.
explain declining
subduction makes the seafloor and oceanic ridges narrower due to converging tectonic plates, forms trenches, volcanic island arcs, and coastal mountain ranges.
explain terminal
ocean basins become narrow and shallow due to sedimentation. young mountain ranges are formed along the sides
explain continental collision
remaining seafloor is eliminated and continents collide, forming a continental mountain chain. High mountain belts are formed
what is continental shelf
continental landmass that is covered by sea. slops gently away from land, rich in biodiversity.
what is continental slope
edge of a continental shelf where the seafloor suddenly drops. Where landslides, turbidity, currents, and sediment slumps are active.
what is continental rise
base of a continental slope where the gradient is shallower. Sediments move down and pile up at the base and is gently sculptured by slow moving current.
what is abyssal plains
vast expanse of terrain that is flat, cold, and dark since no light can penetrate through this depth. Only ultra-fine particles of clay and microscopic marine organisms can reach this depth. These spread out to form thin layers on the seafloor. They survive through chemicals from deep water vents as an energy source
who unified the continental drift theory and seafloor spreading theory
tuzo wilson
what is tuzo wilsons theory known as
plate tectonic theory
go under one plate and sink into the asthenosphere. It turns into magma and gives a rise to volcanoes and volcanic island arcs.
subduction plates
plates split into continental and oceanic. Crust becomes stretched, fissures appear, and crustal block collapses downward
spreading plates
extremely long depression that develops along divergent boundaries (continental crust)
rift valley
what is formed in occeanic crusts when plates separate
mid-ocean ridges
fold or form faults on the crustal rocks. The collision causes great pressure on each other.
Converging plates
what happens when the plates crumple and fold
mountain ranges are created.
