GCSE Geography

Salt marshes are the areas of land which the sea has flooded, between high and low tide. The case study for salt marshes is Key Haven Salt Marsh. Key Haven Marsh is located behind Hurst Castle Spit, on the south Coast of England.

Many salt marshes form behind a bar or spit, because they shelter the marsh. The marshes are made from soft mud and rocks from erosion. 

The salt water from the sea mixes with the sediment in the area an forms a thick  mud, Which provides a very unique environment which some animals can only live in, like the oyster catcher, and some types of butterflies and spiders. Also in the area are sea lavenders, which grow here once the process of vegetation succession has taken place. This is where the plants that are most able to tolerant salt live near to the sea and help to solidify the ground, bringing the soil together. This makes the soil suitable for other none salt tolerant plants to grow on the marsh, making the soil more fertile.

The first plant to grow in a salt marsh, which is nearest the sea, is known as a pioneer plant, which could be something like cord grass.

Key Haven Salt Marsh is retreating by 6 meters a year. in 1989 a storm in December damages part of the spit, by pushing part of the shingle over the top of the salt marsh. This exposed almost 80 meters of the marsh to the full force of the sea. Over 3 months a large amount of the marsh was subject to erosion, destroying part of the marsh.

Conservative Plate Boundaries are when 2 plates move in the same direction, at different speeds. An example of this is at the San Andreas fault in the USA, which is when the Oceanic Pacific plate rubs against the Continental North American Plate.

At this type of plate boundary you get earthquakes, as the plates move and lock together. You don't get other land forms forming, as you don't have magma coming to the surface, and no land is made or lost from this action 

A destructive plate margin is where you get an oceanic plate colliding into a continental plate. This Causes the subduction of the the heavier, denser, oceanic plate under the light, granite continental plate. when the plates collide they can form fold mountain ranges like the Andes. The Case study for the destructive plate margin is the Nazca and South American plate boundary.

You can also have 2 continental plates moving towards one another, which can form fold mountain ranges Like the Alps. This type of fold mountain is formed when the plates force sediment up.  

At this plate boundary land is lost, as rock is destroyed through melting in the mantle. Volcanoes and earthquakes also occur here.

Constructive plate boundaries form when magma rises to the surface an cools to form new rock. this happens as the plates move apart from one another an. this happens at the mid atlantic ridge.

Volcanic islands such as iceland form on this kind of plate boundary. Volcanoes form on land and under the sea  at this type of boundary, as well as earthquakes which can happen on this type of plate boundary but are not as comman 

(Mr) Shield Volcanoes are low lying volcanoes with frequent eruptions, although they are only small. the magma which happens during eruptions is runny, viscous lava. Shield volcanoes like man-a-low-a have only one vent and have a very wide base.

Campsite or Composite volcanoes are have tall, steep sides. the bases are narrow and they have large, infrequent eruptions. a composite volcano like mount saint Helen's can have two vents and has thick magma.