restless earth Flashcards
Describe the structure of the arth from outwards in
crust -> Mantle -> Outer Core -> Inner Core
Describe the outer and inner core
Outer Core
liquid radioactive iron and nickel
Inner Core
solid radioactive iron and nickel
Compare the density of the oceanic and continental Crusts
Oceanic is very dense
Continental is less dense
Compare the age of the oceanic and continental Crusts
Oceanic less old (200 million years)
Continental very old (3.8 billion years)
Compare the Rock type of the oceanic and continental Crusts
Oceanic Basalt
Continental Granite
Compare the depth of the oceanic and continental Crusts
Oceanic is 6-10km (less deep)
Continental is 20km (more deep)
Which crust can be destroyed and which can’t?
Oceanic can be destroyed and renewed
Continental can’t be destroyed
What forms at a collision boundary?
Fold mountains
earthquakes
What forms at a Constructive boundary?
volcanoes
What is wegners theory?
that the Earth’s continents were once joined together, but gradually moved apart over millions of years.
What evidence did wegner have for his theory?
- fossils of very similar plants and animals found on opposite sides of the Atlantic ocean
- ‘jigsaw fit’ with the the coast of south America and Africa
- matching layers of rock in both continents
What forms at a Destructive boundary?
- fold mountains
- ocean trenches
- volcanoes
- earthquakes
What forms at a Conservative boundary?
- earthquakes
- ridges and faults
How are fold mountains formed at collision boundaries?
The plates push layers of accumulated sediment in the sea into folds between them.
How are fold mountains formed at destructive boundaries?
pressure from the subduction of the oceanic plate causes crumples and folds in the continental crust
How are ocean trenches formed?
the oceanic crust is subducted leaving a ‘v’ shape
What is dome volcano?
- vicous lava
- regular eruptions
- e.g. mnt st Helens
Where are dome volcanoes found?
Destructive plate boundary
What is Shield volcano?
- Runny basaltic Lava
- Not explosive
- e.g. Hawaii
Where are Shield volcanoes found?
Constructive plate boundary
What is Composite volcano?
- Viscous lava
- periodic explosive eruptions
- e.g. Mnt Versuvious
Where are Composite volcanoes found?
destructive plate boundary
How are volcanoes formed?
Volcanoes are formed when magma from within the Earth’s upper mantle works its way to the surface. At the surface, it erupts to form lava flows and ash deposits. Over time as the volcano continues to erupt, it will get bigger and bigger.
How are volcanoes monitered?
- Gas emission
- Seismic activity
- Geological observations
How are super volcanoes formed?
- Rising Magma pools under the surface, unable to escape, this forces the ground upwards
- Eventually the crust cracks causing an eruption
- the empty magma chamber refills and the crust forms a caldera. the cycle begins again
How do tsunamis form?
when an earthquake, volcano, landslide or military explosion displaces the water water above it.
How is height gained of a tsunami wave?
when the wave reaches the shore and friction builds up slowing the base as the water behind continues at the same pace forming a crest
Where can earthquakes occur?
at any plate boundary
How do earthquakes form?
- Rocks moving past each other builds up pressure.
- T energy and pressure is suddenly released in seismic waves that ravel through the earth in many different directions shaking everything
What is the epicentre?
the point of the ground that is directly above the focu
What is the focus?
the point where the waves started
What are primary waves?
fast up and down motion (longitudinal)
What are Secondary waves?
Slower side to side movements (transverse)
What is the Richter scale?
- measures the magnitude of an earthquake
- logarithmic
- measured with a seismometer
What is the Mercalli scale?
- shows the effect of the earthquake
- Measured with a key and your eyes
- subjective
How do you prepare for an earthquake?
organising activities + drills
How do you protect against earthquakes?
construct earthquake proof buildings
How do you predict earthquakes?
Attempts to forecast an event
