Geography EOY

Natural Event - an event or proccess that happens naturally

Natural Hazard - a natural event whcih has the potential to threaten life and/or property

Natural Disaster - 10 or more deaths & 100 or more people affect, or state of emergency declared

Hazard Risk - The likelihood that a particular type of hazard will occur in a specific location

Tectonic Hazard- involve movement of tectonic plates in the Earth's crust eg tsunamis, volcanic eruptions, earthquakes

Atomspheric (Climatic) Hazard - associated with the weather or climate eg tornadoes, cyclons, hurricanes, droughts, floods, forest fires

Geomorphological Hazard - linked to the Eath's surface eg landslides

Biological Hazard - involve living organisms eg COVID-19

Factors that affect hazard risk - urbanisation, climate change, poverty, building on floodplanes (when a river floods it deposits fertile silt on its floodplain, which is good for farming; many people can live on this flat land, as it is easy to build houses on it). 

Why do people make themselves vulnerable:

Can't accurately predict hazard: location, magnitude, timing

Can't move: expense, lack of knowledge, language barrier

Don't want to go: overconfident in defences, optimistic it won't happen

It's worth staying: recources, jobs

The inner core is the in the centre and is the hottest of the Earth, it is solid, is made up of iron and nickel and is under extreme pressure

The outer core is the layer that surrounds the inner core, it is liquid and is also made up of iron and nickel

The mantle is the thickest section of the Earth, it is made of a sold material of semi-molten rock and magma, and flows very slowly 

The crust is the outermost larger of the Earth, it is very thin compared to the other layers, it is a solid rock layer. There are two types of crust continental and oceanic. It is made up of thick tectonic plates

Tectonic Plates - the crust and the upper mantle form a rigid shell a tthe surface of the Earth called the lithosphere. The lithosphere is broken into several major fragments, called tectonic plates which move very slowly over the upper mantle. The movement can be tracked using GPS in space. 

Movement of tectonic Plates - the theory of plate tectonics

It was first believed that convection currents in the mantle slowly moved the crust around. It is now thought that a mechanism called ridge push and slab pull drives the movement of tectonic plates. Slab pull occurs where older, denser tectonic plates sink into the mantle at subduction zones. As these older sections of plates sink, newer and less dense sections of plate are pulling along behind. Sinking in one plate leads to plates moving apart in other areas.

Plate Margins / Boundaries - where two plates meet

Oceanic Crust - thin, dense, can be subducted, younger

Continental Crust - thick, less dense, older

Most volcanoes and earthquakes are found at plate margins. Earthquakes are found in all three plate margins whereas volcanoes are only found in constructive and destructive. 

A large band of earthquakes and volcanoes circles the Pacific Ocean, known as the Ring of Fire. 

Not every earthquake or volcano lie along plate margins, some appear in the middle of plates, these are called hot spots, where the Earth's crust is thought to be particularly thin. Eg Hawaii was formed from volcanic eruptions away from the plate margin

At a constructive plate margin the plates move apart from one another. When this happens the magma from the mantle rises up to make (or construct) new land in the form of a shield volcano. The movement of the plates over the mantle can cause earthquakes.

1. the plates move apart

2. magma forces its way to the surface

3. as the magma breaks through the overlying crust, it causes earthquakes

4. on reaching the surface it forms volcanoes

5. the larva is very hot, fluid and it flows a long way before cooling, resulting in broad, flat sheild volcanoes

At a conservative plate margin, the plates move past each other or are side by side moving at different speeds. As the plates move, friction occurs and plates become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released, it sends out huge amounts of energy, causing an earthquake. The earthquakes at a conservative plate boundary can be very destructive as they occur close to the Earth's surface. There are no volcanoes at a conservative plate margin.

1. the two plates are moving past eachother, or at the same direction at different speeds

2. friction between the plates then causes earthquakes

3. earthquakes happen as the stresses gradually build over many years

4. pressure is released suddenly when the plates slip and shift

there are NO volcanoes because there is no magma and no land is lost or gained. 

A destructive plate margin usually involves an oceanic plate and a continental plate. The plates move towards one another and this movement can cause earthquakes.

As the plates collide, the oceanic plate is forced beneath the continental plate. This is known as subduction. This happens because the oceanic plate is denser (heavier) than the continental plate.

When the plate sinks into the mantle it melts to form magma. The pressure of the magma builds up beneath the Earth's surface. The magma escapes through weaknesses in the rock and rises up through a composite volcano. The volcanic eruptions are often violent, with lots of steam, gas and ash.

 1. convection currents brings the plates towards each other                                                           2. this causes friction leading to sysmic waves and earthquakes                                                       3. the oceanic plate is move dense and so will subduct, and will rub against the continental plate 4. the subduction will cause friction and heat, melting the oceanic crust, forming a trench            5. extra pressure in the mantle, stored in the magma chamber, is released as a volcanic eruption

Composite volcanoes are steep, with sticky acidic larva, found out destructive plate margins.