Tectonics Flashcards
(22 cards)
What is the structure of the earth?
Inner core, outer core, mantle (aesthenosphere at top), crust (lithosphere)
What was Alfred Wegener’s theory of continental drift?
1912 - proposed theory that Earth’s tectonics plates have moved throughout history.
What did Wegener think the continents were like 200 million years ago?
That they were all joined up in one large supercontinent - ‘Pangaea’
What did wegener think the continents were like 180 million years ago?
Split into North (Laurasia) and South (Gondwanaland)
What are the continents like now?
All separated, some have small bits linking them together.
Give any 3 pieces of evidence to support Wegener’s theory.
- Identical fossils laid down at exactly same time now exist in different places, if you match them all up, you get a certain shape (could be coincidence, not that exact shape)
- Rocks of similar types, age, formation, structure have been found on opposite sides of Atlantic
- Climatological evidence e.g. oil in Antarctica - comes from trees but Antarctica can’t currently grow trees coz of climate
- Topographical - mountain ranges contain similar rock types and when using the Pangaea map, mountains line up into 1 major range
What are convection currents in magma?
Extreme heat from the inner core is transferred to the outer core to the mantle. The heat in this layer rises, causing molten rock to rise towards the crust. It starts to cool and sink to the sides.
What is a constructive plate boundary?
When 2 plates move in opposite directions. This creates volcanoes, earthquakes and thin, runny magma.
What is a destructive plate boundary?
When an oceanic crust moves towards a continental crust. The oceanic crust is pulled into the mantle by slab pull. This creates violent volcanoes, earthquakes, ash and thick magma. (Rebounds when pulled down enough)
What is a collision plate boundary?
When 2 continental plates move towards and push each other up. This creates huge fold mountains and violent earthquakes.
What is a conservative plate boundary?
When 2 plates move in the same direction at different speeds. When they latch onto each other, pressure is built. When released, it creates severe earthquakes.
What is a shield volcano?
Formed at a constructive plate boundary, magma rises up through cracks, erupts, cools, makes crust. Over time, enough crust created to make volcanoes. Eruptions less explosive, runny magma constantly escaping, lava flows further away from main vent.
What is a composite volcano?
Formed at a destructive plate boundary, friction makes oceanic plate heat up as it’s subducted, melts to make magma, that pools and creates magma chamber. Magma rises through cracks in crust, when it reaches surface, volcano created. Lava thick, acidic, doesn’t flow very far away. Erupt violently as lava blocks vents.
How is an earthquake formed at a destructive boundary?
Friction created when 1 plate subducts under other (vertical movement). The other plate’s end is being pulled down with the other and will eventually flip up, causing an earthquake and mabye a tsunami if under water. These are the worst types of earthquake.
How is an earthquake formed at a conservative plate boundary?
Friction created- 2 plates are moving against each other in the same/ opposite direction.
What is the 1 primary impact of an earthquake?
The ground shaking
Give 3 possible secondary impacts of an earthquake
Landslides, avalanches, collapsing buildings, tsunami, rupturing gas/water pipes (floods, fires), disease due to little sanitation/ crowds in camps/infections/food/water, liquefaction (liquid in ground rises to top - quicksand effect), roads/bridges/airports broken - can’t get help.
How is an earthquake formed?
1.Rock pushes into each other - pressure.
2. Pressure too much - one part of rock slips up-energy released.
3. Seismic waves. Travel through earth all directions.
4. Rock settles into new position - aftershocks (mini earthquakes)
What is the focus of an earthquake?
The point where the seismic waves started.
What is the epicentre of an earthquake?
The point directly above the focus on the earth’s surface.
What are the 3 types of seismic waves?
P-wave : primary, fastest, only some animals feel, pushing action
S-wave : Secondary, Slower, Shearing, pulling, Stronger than P, only travels through Solids - lithosphere, wouldn’t feel in sea
L-wave : most of the damage, goes across earth’s surface, wouldn’t feel in sea
What were the impacts and management of the Haiti 2010 earthquake?
Lost abt 220,000 lives at first but around 300,000 total. Magnitude of 7, 25 km from the capital - Port-au-Prince. There was a local tsunami, a cholera outbreak and many landslides. They already had poor infrastructure, lack of money, poor governance and poverty.
