Plate tectonics Flashcards
What is pangea
Some continents fit together like a geological jigsaw
puzzle. All the rocks were formed when the land was a single continent – Pangea
What is continental drift
The idea that continents are slowly shifting their positions is called
Continental Drift
What are plate tectonics
The earth’s crust is made up of a number of large plates that are moving in constant slow motion.
Convection currents in the mantle move the plates from a source of heat that drives them called radioactive decay.
The ocean floors are continually moving
When was pangea formed
200 million years ago
Characteristics of convection currents.
At the core the temperatures are 5500
Rock nearest the core is heated in the mantle and becomes less dense
Molten rock rises upwards
Temperatures in the upper mantle are cooler and molten rock cools
evidence supports Plate Tectonic Theory
(fossils)
Similar fossils are formed on different continents
Species could not have crossed the ocean so the land must of been closer together.
evidence supports Plate Tectonic Theory (geological patterns)
Similar rock layers is evidence that the rocks were once close
evidence supports Plate Tectonic Theory
Palaeomagnetism
As lava cools the magnetic iron points to the north pole.
It was known at the time that the earth’s polarity switches approximately every
100mill years and when this reversed from north to south, the iron particles in the
erupting magma aligned themselves with the Earth’s new polarity at that time – this
creates evidence of seafloor spreading.
why earthquakes and volcanoes are found along plate boundaries
Eathquakes and volacnoes mainly happen at convergent (destructive) boundaries and divergent (constructive) boundaries
Earthquakes and volcanoes happen at convergent boundaries because…
The powerful convection currents are slowly moving to place together at roughly 4Centimetres per year. The nazca plate is very dense (oceanic rock) and the south American plate is less dense (continental rock) as they collide, friction between the two plates causes violent earthquakes and melts the descending oceanic plate. Then subduction zone occurs. The pressure of the magma rises in the mantle and is forced up. After Time, the pressure builds up and a violent, explosive volcano erupts.The volcanoes are very violent as they have high silica levels due to the mountain of oceanic rock and absorbtion of gases. Whether oceanic plate is forced downwards, it creates very deep oceanic trenches.
Earthquakes and volcanoes happen at divergent boundaries because…
Powerful convection currents within the mantle are slowly moving two plates apart at approximately 2 cm per year. For example, The North American and Eurasian plate are the diverging.I get the peers in the class as the two plates move apart. The mantle move upwards and as the pressure decreases, the upper part of the mantle starts to melt. Magma rises steadily through the gap in forms shield volcanoes and small, but frequent, earthquakes. The volcanoes are frequently and not violently because the lather has a low silica level meaning it has a low viscosity level. As the magma calls, it solidifies and creates new land.New crust is formed under the Atlantic Ocean and even islands are formed over millions of years. These tectonic processes are happening the full length of the Atlantic Ocean and are responsible for creating the mid-Atlantic Ridge.
Where was the Montserrat volcano
In between the Caribbean and South American plate surrounded By other islands.
The reason there is such an explosive volcano in Montserrat
The Caribbean plate and the Atlantic plate created a destructive plate Boundary. the oceanic plate Is then pushed under (subducted) the continental plated as it is more dense and heavy.
How far did the population fall from the eruption in Montserrat
12,000 to 3000 due to the risk (primary)
What was destroyed in the eruption in Montserrat
Over 20 villages (2/3rds of buildings were destroyed).
