Restless Earth Flashcards
Name the 4 layers of the Earth
Inner core, outer core, mantle, crust
Name 3 of the earth plates
Any from: North American, South American, Eurasian, Pacific, Indo Australian, Antarctic, African, Nazca
Name the 4 types of plate margin and the direction they move
Destructive subduction- oceanic subducts beneath continental, Destructive collision- 2 continental plates collide, Constructive- 2 plates move away from eachother, Conservative- 2 plates slide past each other
What do the 4 types of plate margin create?
Destructive subduction: Volcanoes&earthquakes, Destructive collision: Volcanoes&earthquakes, Constructive: Volcanoes, Conservative: Earthquakes
What are the differences between oceanic crust and continental crust?
- Continental crust is older
- Oceanic crust is denser
- Continental crust cannot be renewed or destroyed
What determines the direction of plate movement?
Convection currents within the mantle
How are volcanoes formed at destructive subduction margins?
- Oceanic plate is subducted beneath continental plate
- The friction between the plates builds pressure which causes and earthquake
- The friction also causes the plate to melt and become magma
- The magma is then forced upwards by the earthquake-causing a volcanic eruption
How are volcanoes formed at constructive margins?
- Convection currents cause 2 oceanic plates away from eachother
- As they move apart, hot magma rises and solidifies forming an underwater volcano
- These often become islands
How do earthquakes occur at conservative margins?
- Convection currents force an oceanic plate and a continental plate past eachother
- As they slide past they catch, causing pressure to build
- The pressure is then released, causing an earthquake
What are the highest places on Earth?
Fold mountains
What arre the deepest places on Earth?
Ocean trenches
How are fold mountains formed?
- Geosynclines (depressions on ocean floor) are filled with layers of sediment,deposited by the ocean
- The layers of sediment are compressed and become sedimentary rock
- The plates are forced together at a destructive margin
- The sedimentary layers are forced upwards into fold mountains
How are ocean trenches formed?
- They’re formed at destructive subduction margins when two plates subduct (either oceanic continental or oceanic oceanic)
- As the plates subduct the ocean trench is formed
What are the 4 things people use the Alps for?`
- Mining- minerals and metals
- Farming- dairy
- Hydro Electric Power (HEP)- river water
- Tourism- skiing, lakeside resorts, hotels, restaurants
Name the features of a composite volcano?
- Viscous (thick) lava
- Steep sided/tall
- Highly explosive
- Lots of pyroclastic surges
- Irregular eruptions
- Destructive margins
Give an example of a composite volcano
Mt St Helens
Name the features of a shield volcano?
- Basalt (runny) lava
- Gentle sided/flat
- Non explosive
- No pyroclastic flow
- Regular eruptions
- Constructive margins
Give an example of a shield volcano
Mauna Loa, Hawaii
The date of the Mt St Helens eruption?
18th of May 1980
Location of the Mt St Helens eruption?
Mt St Helens, Cascade Mountains, Washington State, USA
What was the cause of the Mt St Helens eruption?
An earthquake causing a landslide on the north east side of the mountain, caused a cryptodome to explode leading to a lateral blast
What were the effects of the Mt St Helens eruption (primary and secondary)?
Primary: Pyroclastic flow, Truman’s cabin destroyed, 27km wipeout zone, forests uprooted, ash and debris fall into Toutle River and Spirit Lake, 57 killed
Secondary: 3 million tourists now visit, lahars, ash and debris in river and lake destroys habitats, ash clogged air conditioning and blocked roads
What were the immediate term and long term repsonses to the Mt St Helens eruption?
Immediate: Film crews flock to mountain, America declares a state of emergency, army search for survivors, helicopters rescue people, all planes are grounded, 2 million gas masks given out
Long term: USGS now monitor the volcano, 8km exclusion zone set up, 3 million tourists now visit every year, river had to be cleared to prevent flooding
How to USGS now monitor Mt St Helens?
GPS Systems (satellites detecting earth movements), Tiltmeters (identify small changes in the landscape- like a spirit level), Seismographs (detect tremors/earthquakes), Spectrometers (measure sulphur dioxide), Digital Cameras (can create time lapses of the growths)