Plate Tectonics
What is the difference in the composition, thickness, and density of continental and oceanic lithosphere.
Oceanic lithosphere- dense, thin, and mafic
Continental lithosphere- less dense, thick, and felsic
What is an earthquake?
Sudden sliding and breaking of rock along a fault releasing energy/ Earth shaking caused by a rapid release of energy.
What is a tsunami?
Seismic sea waves that occur from earthquake changing the sea floor.
What is a vent at which molten rock, pyroclastic debris, gas, and aerosols erupt at Earth's surface.
A volcano
Which composition of lava has the lowest viscosity?
Mafic (Basaltic)
Explain how positive and negative anomalies in the seafloor occur and the difference between them.
As rocks form at the MOR the minerals in them align with the Earth's magnetic field. As magnetic reversals occur, the mineral alignment changes. Positive anomalies represent areas of the seafloor magnetized in the same direction as the current magnetic field, while negative anomalies represent areas magnetized in the opposite direction (reversed polarity) as the current magnetic field
What is stick-slip behavior?
Motion of the crustal blocks in a fault is stopped by friction and energy builds up until it can overcome the friction and it rapidly moves
Explain the difference between the hypocenter and epicenter of an earthquake.
Hypocenter (focus)- the spot within the earth where earthquake waves originate
Epicenter- the location on the surface of the earth closest to the energy was released below ground
Pahoehoe and A'a' are what composition? What is the difference between the two?
Mafic/basaltic. The texture is different. Pahoehoe have smooth ropy surfaces from where they cooled as the lava was flowing. A'a' has rough surfaces.
What volcano shape is associated with basaltic lava?
Shield
Describe the three types of plate boundaries.
Divergent- two plates moving away from each other
Convergent- two plates moving toward each other
Transform- two plates sliding past each other
What is the difference between a dip-slip fault, strike-slip fault, and an oblique fault?
Strike-slip- if there is no dip, the fault is vertical – the blocks move laterally (lateral shear)
Dip-slip- have a vertical slant (normal, reverse, and thrust faults) where the hanging wall moves either up or down relative to the footwall
Oblique faults are a combination of both- they move diagonally
Explain liquefaction.
Ground shaking from earthquakes causes the sediment and structures on top of a layer of wet sand and silt (quicksand) to "settle out" or sink.
What are the differences between dormant, extinct, and active volcanoes.
Dormant- Have not erupted for hundreds to thousands of years but could erupt again.
Active- Are erupting, recently erupted, or are likely to erupt soon.
Extinct- Will never erupt again because the cause of volcanism no longer exists.
Explain the difference between effusive and explosive eruptions.
Explosive- forcefully emits pyroclastic debris
Effusive- lava pours out of a vent or fissure
What is apparent polar wander?
The idea that Earth’s poles moved over time and could be mapped using paleomagnetism.
What is the mechanism for plate tectonics?
Ridge push and slab pull.
What are the four types of seismic waves? Which are body waves and which are surface waves?
P-waves=compressional body waves
S-waves= shear body waves
Love waves= surface wave with snake-like movement
Rayleigh waves= surface wave with that cause ripple motion
How do geologists predict volcanic eruptions? (4 things)
Earthquake activity, changes in heat flow, changes in shape, and increase in gas and steam emissions.
What are the biggest threats that result from explosive volcanic eruptions?
Pyroclastic flows and lahars.
What are the 5 arguments Wegener used to support his hypothesis of continental drift?
A. The fit of the continents
B. Locations of past glaciers
C. Distribution of climatic belts
D. Distribution of fossils
E. Matching geologic units
What is continental rifting?
When continental lithosphere stretches and thins, the upper crust breaks by faulting. The upwelling asthenosphere initiates volcanism. Rifting may split a continent in two.
What are most injuries and death during Earthquakes caused by?
Structures and debris collapsing on people (not ground shaking)
Why do some volcanic eruptions mostly produce lava flows and others produce lahars, ash, pyroclastic flows, etc.
The composition of the magma in the volcano determines if it is explosive or effusive. Mafic magma produces mostly low viscosity basaltic flows while felsic magma is highly viscous and the pressure build up produces pyroclastic flows, ash, and other explosive material.
What is the difference between an island volcanic arc and a continental volcanic arc?
An island volcanic arc forms when one oceanic plate subducts beneath another oceanic plate, creating a chain of volcanic islands in the ocean, while a continental volcanic arc forms when an oceanic plate subducts beneath a continental plate, resulting in a chain of volcanoes along the edge of a continent