Unit 9 Flashcards
What is continental crust
Layers of igneous, sedimentary and metamorphic rocks, that form, geological continents, a.k.a. landmass and their continental shelves
Oceanic crust
The layer of igneous rock that forms at the base of the ocean floor
Mantle
Layer of silicate rock between the rigid crust and the outer core. It’s made up of several layers that are all ultramafic (low silica)
Core
Outer core liquid inner core solid due to intense pressure, 95% iron 5% nickel
What is seismology?
The study of vibrations on and within the earth or seismic waves.
What are surface waves?
These radiate along our surface, and they form when a body wave reaches the surface
What are body waves?
These propagate through earth, and their most useful for understanding our interior. Usually all waves are caused by earthquakes including surface waves.
What is a compression wave or P wave?
These are compression waves they’re like a slinky material compresses as the wave moves past it, and they are the first wave to be detected
What are sheer waves?
These arrive after the pew waves material, vibrates as the wave moves past and it looks like a hair curl very loose
What are the two body waves?
P Aves waves or compression waves, and S waves, which are known as sheer waves
How are body waves affected by the state of the rock
We velocities increase with density, so compression waves are slow down in liquid medium, where sheer waves cannot travel through liquid. Usually this means S waves can’t go through the core.
What is the shadow zone?
Essentially where the S waves could not go through the core and what areas were not hit
How does internal temperature change with depth?
Temperature increases with depth
What is mantle convection
Heat from the core is being brought towards the surface faster so it’s heating the lower mantle material near the source gets hot, which expands and rises think of boiling water. Convection is the outer core trying to reverse the magnetic field.
What is responsible for earth magnetic field
He is transferred from the solid, inner core to the liquid, outer core and the convection of liquid iron in the outer, core, conducts, electricity, and its motion generates a magnetic field
What does isostacy
This is the rising or settling of a portion of earths solid crust that occurs when weight is removed or added, maintaining equilibrium between buoyant forces by pushing the crust up and gravity, pulling it down
Isostatic vs nonisostatic
Heavier matter will sink deeper vs matter not sinking at all
What is continental drift?
The theory that earths continents have moved over geological time relative to each other, appears as if they have drifted across the ocean
Palaeomagnetism
Earths magnetic field, magnetic field behaves, as if there was one giant magnet at the core. When magnetic materials, cool, they become digitized parallel to earth magnetic field at the time, so they retain remanent magnetism.
What is inclination and declination regarding earths magnetic field?
Inclination is the steepness/the ankle and declination is the direction 
Remnant magnetism
The inclination and declination of the magnetic field can tell you the orientation and latitude at which the deposit was formed. This is how we track migration of continents around the globe.
Why is remnant magnetism of the ocean floor striped?
New ocean floors, hypothesize to form at sea floor, spreading bridges, a.k.a. mid ocean ridges, so it pushes older sea floor away on either side, which creates a mirror
Plate tectonics
The theory that explains how major landforms are created as a result of earths mantle convection. Plates are constantly moving in different directions.
Divergent plate, boundaries
Plates are moving away from each other
Convergent plate, boundaries
Plates are moving towards each other
Transform plate boundaries
Plates are moving against each other
Mid ocean ridges
Two lithospheric plates are moving away from each other so divergent. This creates basalt deposits, which are mafic extrusive rocks. These are generating new seafloor.
Ocean to ocean plate boundaries
Two plates of oceanic crust push against each other. This oceanic crust is thin and dense so one played will subduct beneath the other. Usually the older/colder/denser plate will sink. Water is released during subduction, which leads to flux melting. A buoyant magma moves towards the service to create a chain of volcanic islands.
Oceanic to continent plate, boundaries
Oceanic crust is pushing against continental crust, the oceanic plate will subduct because it is denser than continental crust. The continental crust crumbles up or thickens, which creates the mountain. The melting of this oceanic plate leads to magma plumes, that result in composition volcanoes.
Continent continent plate, boundaries
Continental crust, colliding with another continental crust. Both plates are buoyant, or felt sick, so neither will subduct no volcanos form, because no melting of material subducted into the mantle, a thick crumbles zone develops, which creates large mountains
Transform plate boundaries
One plate slides past another plate without production or destruction of crystal material usually their ocean to ocean boundaries
What is stress and what does it lead to?
Rocks are subjected to stress due to movement of plates and burial (weight of overlying rocks,) it leads to strain(change in shape or size) which is a rock response to stress
How is stress applied if it’s due to just burial
Stress will be equal in all directions
How will stress be applied if it’s due to burial and tectonic forces
Stress will be unevenly distributed in all directions
Elastic deformation
This is reversible. Once this stress is removed, the rock returns to its original state.
Plastic deformation
Rocks will deform under stress without breaking, essentially bending, and this is permanent
Brittle deformation
Permanent and rocks will break or fracture under. Applied stress.
What are the two different folds?
Syncline, which is U-shaped and the youngest rock are in the middle, and anticline, which is end shaped and the oldest rock are in the middle
What are the parts of a fold?
Fold access or the hinge line this is the line that runs along the nose of the fold or along the bend. Then we have the axle plane which is an imaginary plane that contains the hinge and then the limbs which are the arms of the fold that bend away from the axle plane if it’s anticline or towards the axle plane if it’s syncline
What happens if the hinge line is at an angle on the fold?
It will create something called, plunging folds, and the surface trace of the rocks look like arches
Plunging anticline
Hinge line is at an angle to the land surface rock show a u-shape
Plunging syncline
Looking at it head on you see the newest rock and the in circles around it you see the older rocks
Faults
Result of brittle deformation, where rock breaks in response to applied stress
Fault, trace
Expression of the fault on the land service basically just looking at the fault head on
Hanging wall
This is a block above the fault
Footwall
Block below the fault
Normal fault
The hanging wall drops down and the foot wall moves up
Reverse fault
The hanging wall slides up along the football. This usually occurs in area of compressional stress
Strike slip fault
Steep or vertical faults, where the rock has been moved, horizontally relative to each other, there is no vertical displacement
Strike slip fault
Steep or vertical faults where the rock has moved horizontally from each other no vertical displacement
