GEOGRAPHY PAPER 1 The structure of the Earth The inner core is in the center and is the hottest part of the Earth. It is solid and temperatures of up to 5,500°C. The inner core is like the engine room of the Earth. The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel. It is still extremely hot, with temperatures similar to the inner core. The mantle is the widest section of the Earth. The mantle is made up of semimolten rock called magma. In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt. The crust is the outer layer of the earth. It is a thin layer between 0-60 km thick. The crust is the solid rock layer upon which we live. There are two different types of crust: continental crust, which carries land oceanic crust, which carries water. Plate tectonics The movement of the plates, and the activity inside the Earth, is called plate tectonics. Plate tectonics cause earthquakes and volcanoes. The point where two plates meet is called a plate boundary Different plate boundaries At a tensional, constructive or divergent boundary the plates move apart. At a compressional, destructive or convergent boundary the plates move towards each other. At a conservative or transform boundary the plates slide past each other. Natural hazard Natural hazards are extreme natural events that can cause loss of life, extreme damage to property and disrupt human activities. Types of natural hazard Tectonic hazards occur when the Earth's crust moves. For example, when the plates move, friction can cause them to become stuck. Tension builds until the plates release, which leads to an earthquake. Climatic hazards occur when a region has certain weather conditions, for example heavy rainfall can lead to flooding. Tectonic hazards Climatic hazards Earthquakes Flooding Tsunamis Tornadoes Volcanoes Tropical storms (hurricanes) Mountain avalanches Droughts Volcanoes and volcanic eruptions A volcano is formed by eruptions of lava and ash. Volcanoes are usually cone shaped mountains or hills. When magma reaches the Earth's surface it is called lava. When the lava cools, it forms rock. Volcanic eruptions can happen at destructive and constructive boundaries, but not at conservative boundaries. Some volcanoes happen underwater, along the seabed or ocean floor. How a volcano form: Magma rises through cracks or weaknesses in the Earth's crust. Pressure builds up inside the Earth. When this pressure is released, eg as a result of plate movement, magma explodes to the surface causing a volcanic eruption. The lava from the eruption cools to form new crust. Over time, after several eruptions, the rock builds up and a volcano forms. Coastal processes Destructive and constructive waves Destructive waves Destructive waves are created in storm conditions. They are created from big, strong waves when the wind is powerful and has been blowing for a long time. They occur when wave energy is high and the wave has travelled over a long fetch. They tend to erode the coast. They have a stronger backwash than swash. They have a short wave length and are high and steep. constructive waves They are created in calm weather and are less powerful than destructive waves. They break on the shore and deposit material, building up beaches. They have a swash that is stronger than the backwash. They have a long wavelength, and are low in height. The sea shapes the coastal landscape. Coastal erosion is the wearing away and breaking up of rock along the coast. Hydraulic action: Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion. Abrasion: Bits of rock and sand in waves grind down cliff surfaces like sandpaper. Attrition: Waves smash rocks and pebbles on the shore into each other, and they break and become smoother. Solution: Acids contained in sea water will dissolve some types of rock such as chalk or limestone. Headlands are exposed to the full force of the waves. As they erode they often form distinctive characteristics. The hydraulic action of the waves widens cracks in the rock eventually forming caves. 1. Sand in the waves causes abrasion and eventually the cave may erode completely through the headland to form an arch. 2. Over time the arch becomes wider until it cannot support the top which collapses leaving a stack. 3. The base of the stack continues to be eroded until it collapses and leaves a stump. Coastal transportation The various types of material found in the sea comes from many different sources such as: being eroded from cliffs; being transported by longshore drift along the coastline; being brought inland from offshore by constructive waves; being carried to the coastline by rivers. Waves can approach the coast at an angle because of the direction of the prevailing wind. The swash of the waves carries material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90°. This movement of material is called transportation. Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag. Coastal deposition When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition. Deposition happens when the swash is stronger than the backwash and is associated with constructive waves. Conditions that encourage deposition Deposition is likely to occur when: waves enter an area of shallow water; waves enter a sheltered area, e.g. a cove or bay; there is little wind; there is a good supply of material. Types of weathering Exposed rocks along the coastline can be broken down by the processes of weathering. Freeze-thaw weathering Freeze-thaw weathering occurs when rocks are porous (contain holes) or permeable (allow water to pass through it). 1. Water enters cracks in the rock. 2. When temperatures drop, the water freezes and expands causing the crack to widen. 3. The ice melts and water makes its way deeper into the cracks. 4. The process repeats itself until the rock splits entirely. Biological weathering 1. Plant roots can get into small cracks in the rock. 2. As the roots grow, the cracks become larger. 3. This causes small pieces of rock to break away. Chemical weathering Rainwater and seawater can be a weak acid. If a coastline is made up of rocks such as limestone or chalk, over time they can become dissolved by the acid in the water.
