Chapter 9 Flashcards
Continental drift
When continents split and moved away after millions of years
Seafloor spreading
when new rocky crust forms and spreads outwards
Subduction
Process of crust sinking into the Earth and forming trenches
Tectonic plates
Cracked plates of crust. Float on asthenosphere
How do tectonic plates move?
convection currents
What are convection currents?
Where magma rises and flows under the plates, making currents
What are the types of plate movement
Diverging, converging and transform boundaries
Diverging boundaries
Where plates move apart. Makes mid-ocean ridges and land widening
Converging boundaries
Where plates collide.
What are the three types of converging boundaries?
oceanic - continental, continental - continental, oceanic - oceanic
What does oceanic - continental converging cause?
Mountains and volcanoes. Also causes subduction
What does continental - continental converging cause?
High mountains
What does oceanic - oceanic converging cause?
Deep trenches
Transform boundaries
Where plates slide parallel to each other in the opposite direction. Cause earthquakes
What are fault lines?
Cracks in rocks from transform boundaries
Where are volcanoes usually located?
Near tectonic plates because of weak crusts
What are hot spots?
Isolated weak spots. Occur in chains
What are earthquakes measured by?
A seismometer. Seismic waves - movement of the ground in an earthquake
What are the three types of seismic waves and what are their characteristics?
Primary - Fast
Secondary - Slightly slower
Surface - Slowest but most damaging
What is the focus?
Where the earthquake starts
What is the epicentre?
The point at which Earth’s surface is directly above the focus
What measures earthquakes?
Richter scale
How to stop the effects of earthquakes?
Base isolation isolates the building from the waves
Dampers make the building move in the opposite direction of the waves to oppose the effect
