Harzardous Earth Flashcards
Explain the evidence that support plate tectonic theory.
Jigsaw Fit: The east coast of South America and the west coast of Africa look like they once were connected.
Convectional Currents: hot rock rises in the mantle and then moves in two different directions, which pulls the crust apart. The hot rock, then sinks and gets cooler and brings parts of the crust down, pulling the plates apart.
Study of Fossils: The Mesosaurus fossils were found on the eastern coast of South Ameirca and the western side of Africa. This means that they died in each land then the land split and left the fossils behind distributed across each continent.
Geological Patterns: Identical rocks and mountain ranges I found over the ocean in the continents, meaning they once got torn apart. Glacial striations have also been found in continents that are now warm which means that they could have been connected to Antarctica. Coal has also been found in cold places which must have happened in hot areas, so the continents must have connected up with these geological patterns.
Why are volcanoes and earthquakes found along plate boundaries?
Because all along plate boundaries, the plates are causing stress and friction which is then released to form earthquakes. All while, in subduction areas, magma is building up in the magma chamber due to the melting of the oceanic plate creating magma, which is ready to force its way through a composite volcano.
How do earthquakes and volcanoes occur at convergent/destructive plate boundaries?
Convergent/destructive plate boundaries are the result of a continental plate and an oceanic plate colliding with each other. The oceanic plate is then forced beneath the continental plate. As the plates move against each other friction and stress builds up and when this is finally released an earthquake occurs. Lighter continental crust remains at the surface but crumples into fold mountains, the sediment and water from the continental plate melt in the mantle and form magma and fill the magma chamber. Then magama builds up in the magma chamber and when the pressure builds up the magma escapes through a weak spot which then becomes a composite volcano because the sediment makes the magma viscous so it doesn’t go far creating a tall steep composite volcano.
How do earthquakes and volcanoes form at divergent plate boundaries?
Divergent: convection currents in the mantle drive the plates away from each other and new mantle rises along the opening and creates new crust creating a volcano. The crust is then pulled apart where cracks and faults are made which causes earthquakes. Where the hot mantle cools and falls, it drags the plates down with it creating subduction zones.
How do earthquakes form at conservative plate boundaries?
Conservative: The plates move sideways past each other in a series of jerks. Huge stress is developed in the rock and the plates can lock together due to friction. When this lock is broken the stress is released and this causes and earthquake.
How do earthquakes form at collision plate boundaries?
Collision: When two continental plates collide they both rise as they are the same density. This causes fold mountains to grow when they push together. As the plates push togehter even more they lock together due to friction but when this friction is overcome earthquakes occur due to the stress being released.
What were the effects of the Monserrat volcano eruption?
Lava flows - slow moving magma which destroys everything in its path.
Lava explosions - solidified lava fragments which have been made from magma solidifying creating large lava domes over the volcano which then breaks up when it erupts causing the lava fragments to fall down the mountain.
Pyroclastic flows - fast moving currents of hot gas and rock which move downhill. The pyroclastic flows from Montserrat travelled up to 4km.
Volcanic ash - fragments of lava which are lifted high into the atmosphere and travel great distances in the wind. The wind blew the volcanic ash initially to the south west of Montserrat but it ended up and travelling to the atlantic.
Volcanic bombs - mass of molten rock larger than 64 mm in diameter, formed when a volcano ejects viscous fragments of lava during an eruption which travel many kilometers.
Lahars - mudflow made up of pyroclastic material, rocky debris and water which is hot and travels fast down the side of a volcano even after the eruption has ended.
Overall, the Montserrat had effects on land all around the volcano and more than 15 settlements were destroyed, which were around 4km away from the volcano.
Why did human and physical factors caused the Haiti earthquake to be so destructive?
It was so destructive because:
The magnitude of the shock waves were 7 on the Richter scale.
The depth of the focus was only 8-10 km deep which meant that the earthquake was felt at the surface more causing more destruction.
The location of the epicentre was only 15 km southwest of Port-au-Prince ehich means that it was very close to the capital meaning lots of damge happened on land.
People weren’t prepared as they didn’t get any early warnings as people couldn’t predict it.
How do tsunamis form?
Subduction occurs causing stress on the boundary and the flexing of the plates can cause an earthquake. The plates will suddenly flick past each other and release all of their energy in the waves. As the waves reach the shallower water they will get closer together, taller and slower. The waves move in different directions like a ripple. The tsunami then surges very far inland picking up anything in its way causing mass destruction.
Name the order of the layers of the earth from outer to inner.
Crust
Mantle
Outer core
Inner core
What is the crust?
Thinnest layer, coldest layer, solid rock
What is the mantle?
Thickest layer, 1000°c near the crust 3700°c near the outer core, solid rock that can flow (semi-molten)
What is the outer core?
Approximately 2300km thick, between 3700°c and 5000°c, semi liquid iron.
What is the inner core?
Very dense, hottest part of the earth (5000°c), mainly iron and nickel, it is solid due to the pressure.
Name the different tectonic plates.
On GoodNotes
What features do Divergent plate boundaries cause?
Volcanoes
Earthquakes
What features do Conservative plate boundaries cause?
Earthquakes
What features do Collision plate boundaries cause?
Fold mountains
Earthquakes
What is an earthquake?
Earthquakes are vibrations of the earth’s crust caused by movement at plate boundaries and major fault lines. Earthquakes can occur at all major fault boundaries but the most severe are usually conservative and convergent.