Tectonics Flashcards
Convergent Boundaries
Also known as destructive boundaries, where the denser oceanic plate is thrust beneath the continental plate
Forms a subduction zone
Creates mountains and eruptions
Divergent Boundaries
Also known as constructive boundaries
The moving apart of plates
creates rifts filled with new crustal material from volcanic eruptions
Conservative Boundaries
Two crustal plates slide past each other
Friction triggers earthquakes
Collision Boundaries
Two continental plates collide
Pushes up mountains
Plate Tectonic Theory
Views the earths crust as consisting of a number of mobile yet rigid elements called plates
Low density of thick continental crust allows it to float on the dense mantle below
Adding to the plate tectonic theory, how do plates move?
Heat derived from the earths core rises within the mantle to create convection currents
Define a tsunami
Caused by submarine shock waves generated by tectonic events
Potentially most devastating where a gently sloping continental shelf allows them to get high
Where’s the ring of fire
Pacific ocean
What is a hotspot volcano
Found in the middle of tectonic plates
Occur when the mantle is unusually thin and hot
Example of a hotspot volcano
Hawaiian islands
What is the Benioff Zone
Boundary between an oceanic plate that is undergoing subduction and an overriding continental plate
Three types of wave
P S and Surface Waves
Difference between focus and epicentre?
Focus is the point in the earths crust where pressure is released
Epicentre id the point on the earths surface above the focus
P waves:
First waves to come
Compress and expand the ground
4.8 Km/s
S Waves
Come after P waves
Vibrate up/down and side to side
Surface Waves
Much slower that the others but shake the ground violently
Some make the ground roll like the ocean
What is Palaeomagnetism?
Results from magma locking in the earths magnetic polarity when it cools
scientists use to reconstruct past plate movements
Rayleigh waves and Love waves
Rayleigh waves are circular like a transverse wave
Love waves go side to side on the ground
Secondary Hazards of seismic waves
Liquefaction
Landslides
Tsunamis
What does the impact of a tsunami depend on?
Duration
Wave amplitude/distance travelled
Depth of offshore zone
Degree of coastal protection
Quality of early-warning systems
Density of population near coastline
Primary Hazards of Volcanoes?
Pyroclastic Flows
Tephra
Lava Flows
Volcanic Gases
Primary Hazards of Volcanoes?
Lahars
Jokulhaups
Define Pyroclastic Flows
A dense, fast-moving flow of solidified lava pieces, volcanic ash, and hot gases
Define Tephra
These are ash falls
Rock fragments ejected into the atmosphere regardless of size
This stuff accumulating on roofs means they can collapse
