Tectonics Flashcards
Earthquake
The violent shaking of the earth’s crust.
Earthquake magnitude
The strength of an earthquake.
Earthquake intensity
The violence of earth’s movements produced by an earthquake.
Mercalli Scale
The scale used to measure earthquake intensity (I to XII)
Richter Scale
The scale used to measure earthquake magnitude
Focus
The point in which the pressure is released inside the earth. Often many kilometres down.
Epicentre
The point on the ground surface directly above the focus. Where the greatest damage usually occurs.
Crust
The outer layer of the earth. 0-100km thick
What is the difference between continental crust and oceanic crust?
Oceanic:
Thinner
Newer
Basalt
More dense
Continental:
Thicker
Older
Granite
Less dense
Mantle
The third layer in the earths structure, 100km-2900km deep. Made of molten rock.
Outer core
Second layer in the earths structure, 2900km-5100km thick. Made of liquid iron and nickel.
Inner core
5100km-6378km deep, first layer of the earth.
Convection currents
Heated plumes of magma which create crustal plate movement.
What happens when convection currents diverge and converge?
When they diverge, plates move apart.
When the converge, plates move towards each other.
Plates
Pieces of the earth’s crust
Plate boundary
The point where two tectonic plates meet.
How many major and minor plates are there?
7 major and 8 minor
Where do most of the world’s earthquakes and volcanoes occur?
On or near the plate boundaries.
Hotspots
Areas away from plate boundaries where volcanoes and earthquakes are found.
Where can you find hotspots?
In places where the crust is very thin
Give an example of where a hotspot is.
Hawaii
Where is the largest concentration of volcanoes found and what is its name?
The Pacific Ocean - The Ring of Fire.
What are the 7 major plates called and where are they found?
Magma Chamber
Large underground pool of magma
Lava
Magma once it reaches the surface
Crater
Bowl shaped basin on the top of the volcano.
Vent
Central tube which magma travels through
Secondary cones
Eruptions from other vents may build up secondary cones on the flanks.
Ash/steam/gas
Material thrown out by the force of the eruption.
Volcanic bombs
Larger material thrown out by the force of the eruption.
How are some ways experts can estimate when an eruption is likely to happen?
Seismometers - an instrument that measures ground vibrations caused by a variety of processes.
Gas sensors - an instrument that detects carbon dioxide, sends data continuously via radio to an observatory.
Tilt-meters - when magma accumulates beneath the ground, the slope of adjacent areas will usually tilt away from the centre of uplift.
GPS satellites - detect motion at a volcano before any earthquakes occur.
How are some ways you can prepare for volcanic eruptions?
Evacuation - evacuating all the citizens before the volcano erupts.
Diverting the lava flow - changing the course of the lava to avoid areas of value.
Go bags - a bag of things you need to take in the case of an evacuation.
What are responses?
How countries and communities react to tectonic hazards and other disasters.
What are the two categories of responses?
Short-term/immediate - a response in days or weeks immediately after a disaster has happened. Short-term responses mainly involve search and rescue, helping the injured and providing key supplies.
Long-term - responses go on for months and years after a disaster. It involves rebuilding destroyed houses, schools, hospitals, etc. It also involves kick-starting the local economy.
What are the three types of impacts?
Social - direct impact on people.
Economic - impact on economic activities such as businesses.
Environmental - impact on the landscapes including water and air pollution.
Describe what happens on a constructive margin.
When plates move apart, magma from the mantle rises to construct new land in the form of a shield volcano.
Describe what happens on a destructive margin.
Usually involving an oceanic plate and a continental plate, they move towards each other, and at the collision, the oceanic plate subducts as it is denser. The plate melts in the mantle to form magma, which then escapes ad rises through a composite volcano (formed).
Describe what happens on a conservative margin.
The plates are moving past each other or are moving side by side at different speeds. Friction occurs and the plates get stuck. Pressure builds up, and when the pressure is released, it sends out huge amounts of energy causing an earthquake.
Describe what happens on a collision boundary.
Involving two continental plates, neither can sink so the goo upwards to form fold mountains. Earthquakes can occur.
