What are Earthquakes and Volcanoes
Earthquakes
Onderdelen in deze les
Earthquakes
When two plates push against each other (in any sort of direction) – there is immense pressure – this usually causes the earth’s crust to crack (called a fault). The fault can be the actual plate boundary, or close to it. In some places the plates get locked together. The energy has to go somewhere - so it gets stored in the rocks strain energy (strain means to deform due under pressure).
Earthquake Epicenters:1963-1998
What scale measures earthquake magnitude?
Fahrenheit scale
Beaufort scale
Richter scale
Celsius scale
Where do most earthquakes occur?
Along tectonic plate boundaries
At the Earth's core
Above sea level
In the ocean depths
Which country experiences the most earthquakes?
Canada
Japan
Brazil
Australia
Volcanoes
There are 4 places where we find volcanoes
1. They happen at constructive boundaries (SEPARATION)
Lava spreads out easily - flows over a large area - when on land Create shield volcanoes
Which movement creates new oceanic crust?
Convergent boundary movement
Subduction zone activity
Divergent boundary movement
Transform boundary movement
2. Destructive boundaries. (COLLISION)
CO2 Gas released from the melting limestone expands and makes holes in the crust.
Highly explosive volcanoes!
Earthquakes also help to make cracks in the crust
3. When 2 Oceanic crusts collide (same crust)
South Pacific you’ll notice that there are a lot of small volcanic islands .
When two plates carrying oceanic crust collide, it creates a different kind of subduction boundary.
When they meet, usually the older of the two sinks - because plates grow colder and denser (heavier) with age. These plates will sink under the other.
4. Hot Spots
The last occurs on places like Hawaii. It is a giant volcano
Not located on any plate boundary!
Normally mantle convection has a rise and fall – in a circular motion. However, in some places like Hawaii and Yellowstone National Park, convection rises as a single plume the result is a “hot spot.”
Hot spot volcanoes often form long chains of islands that result from the motion of the plate over the hot-spot source.
Volcano types
What type of volcano is typically cone-shaped?
Shield volcano
Stratovolcano
Lava dome
Cinder cone
Which volcano type has gentle slopes?
Cinder cone
Stratovolcano
Caldera
Shield volcano
Which type of volcano is most explosive?
Shield volcano
Stratovolcano
Lava dome
Cinder cone
Shield volcano
This is a broad, shallow volcanic cone, which arises because the running lava, which is fluid and hot, cools slowly.
lava flows easily, it can move down gradual slopes over great distances.
2. Composite volcano (Strato Volcano)
These volcanoes are characterized by explosive eruptions. When magma is cooler it is thick and sticky (viscous), which makes it harder for gas bubbles to expand and escape.
The resulting pressure causes the magma to foam and explode violently, blasting it into tiny pieces (volcanic ash).
These eruptions create steep sided cones. They can also create lava flows, hot ash clouds (pyroclastic flows).
3. Caldera volcano
An older volcano with a large crater which can up to (10km) wide. In this crater many little new craters are formed
These erupt so explosively and infrequently that little material builds up near the vent (this means no cone). Eruptions usually have emptied the magma chamber below which leaves the area around the vent unsupported, causing it to sink or collapse under its own weight.
The resulting basin-shaped depression is roughly circular and is usually several kilometres or more in diameter. Although caldera volcanoes are rare, they are the most dangerous.
Crater Lake - USA
Aniakchak – Alaska USA
