Tectonic Hazards Revision

The earth is 4600 million years old

The earth consists of:

-Inner core - solid iron and nickel

-Outer core - liquid iron and nickel

-Mantle - semi-molten rock

-Crust - solid rock, 20km thick, which is seperated into plates

Heat from the radioactive decomposition of minerals in the centre of the Earth creates convection currents in the mantle.

When the convection currents meet the surface, they cause the plates to move. This movement is very slow, about a few centimetres a year. 

Continental:

-Thicker

-Lighter / less dense

-Cannot sink

-Is permanent, meaning is cannot be renewed or destroyed

Oceanic:

-Thinner

-More dense / heavier

-Constantly being destroyed and renewed

-This is a DESTRUCTIVE plate boundary

-A destructive plate boundary is where a continental and oceanic plate meet.

-The oceanic plate is more dense, so it is subducted underneath the continental plate.

-As the two plates scrape together, friction melts the rocks, and this escapes as lava in a violent volcanic eruption, along with severe earthquakes.

-Examples of landforms include: Andes Mountains, Villa Rica volcano (Chile), and the Peru-Chile deep sea trench.

-This is a COLLISION plate boundary

-A collision plate boundary is where two continental plates meet. 

-Because they are the same density, neither sink, so they buckle, forming fold mountains and causing severe earthquakes.

-There is no volcanic acticity at this type of plate boundary.

-Examples of landforms include: Himalayas

-This is a CONSTRUCTIVE plate boundary.

-A constructive plate boundary is where two plates move apart. As they do so, a gap is formed, allowing lava to escape, making gentle volcanic eruptions and less violent earthquakes.

-Examples of landforms include: Mid-Atlantic Ridge, Mauna Loa (Hawaii), East-African rift valley, and Iceland

-This is a CONSERVATIVE plate boundary.

-A conservative plate boundary is where two plates move past each other, along a fault. 

-No volcanoes are found here, but severe earthquakes occur.

-Examples of landforms include: San Andreas Fault

-Formed at CONSERVATIVE plate boundaries

-For example: San Andreas Fault

-The San Andreas fault is 810miles long

-It moves 1½ inches each year

-There is predicted to be a magnitude 6 earthquake at the San Andreas Fault, every 22 years

-Formed at COLLISION plate boundaries

-The rocks are forced together, making them crumble and be forced upwards

-For example: Himalayas

-They are formed at DESTRUCTIVE plate boundaries

-When the two plates come together, and the oceanic one is forced downwards, there is a deep part. This is the trench.

-The formation of trenches, causes earthquakes deep under the sea, leading to tsunamis.

-They are formed at CONSTRUCTIVE plate boundaries.

-When the two plates move apart, it causes fractures to form. 

-Along the fractures, the two plates keep mobing apart, and some areas of land formed between fractures can gradually sink.

-Earthquakes tend to occur in these areas

-They are formed at CONSTRUCTIVE plate boundaries

-Two plates moving apart, with a plate boundary in the middle of an ocean, will allow magma to rise from the mantle, causing small volcanic eruptions, forming a mid-ocean ridge.

-Larger volcanic eruptions, plus an accumulation of smaller ones, can create small volcanic islands in the middle of oceans.

-They all form along the plate boundary.