Sunday, November 4, 2018 GEOGRAPHY UNIT 1-1 - What are natural hazards? Hazards are events that threaten us or cause loss of human life and property, natural hazards are hazards caused by the nature. Type Examples Tectonic Hazards Earthquakes, Volcanic Eruptions, Tsunamis Climatic Hazards Flooding, Drought, Typhoons Geological Hazards Landslides, Avalanches Biological Hazards Pest (Locus), Disease or Bacteria - What are tectonic hazards? A. Sunday, November 4, 2018 Sunday, November 4, 2018 B. Earthquakes The hazard consists of sudden shaking of the land which is caused by sudden release of energy stored in the rocks beneath the earth’s surface. Earthquakes are measured by the Richter scale. which is recorded by a seismograph. Some Examples of Earthquakes: Sunday, November 4, 2018 C. Volcanic Eruptions The hazard occurs when lava, hot rocks debris, ashes and gases are ejected or emitted from an opening in the earth’s surface. Some Examples of Volcanic Eruptions: C. Tsunamis The hazard is caused by a series of big sea waves, traveling in all directions. When tsunamis reach the shallow seas at the coast, they slow down and can tower up to over 30 meters high. Some Examples of Tsunamis: - Why should we be concerned about Tectonic Hazards? Sunday, November 4, 2018 GEOGRAPHY UNIT 1-2 - What is the structure of the Earth? The Earth is divided into three layers, the crust, the mantle and the core. The three layers have diﬀerent temperature, density, thickness and composition. Crust Mantle Core Thickness Thinner (6 -70km) Thicker (2900 km) Thickest (3470 km) Average Density Less Dense (2.7 g/cm ) Denser (3.3 g/cm ) Densest (11 g/cm ) Temperature Cooler (Around 22°C) Hotter (1000-3500°C) Hottest (3500-4500°C) Composition Mainly Silica Iron and Magnesium Iron and Nickel In Conclusion, thickness, average density and temperature of the Earth’s layers increase from the exterior to the interior. The more the centre of the Earth, the thicker, hotter and denser of the layer is. Sunday, November 4, 2018 The Structure of the Earth can be further divided into…. 1. Crust Continental Crust - Makes up the continent and the continent shelves. - Thick and Light Oceanic Crust - Found under the Oceans - Thin and Dense 2. Mantle Uppermost part of the mantle - Exists in solid state - Together with the crust, they are collectively known as the asthenosphere. Asthenosphere - The rocks in this layer are in plastic state. Lower Mantle - Exists in a solid state under high pressure. 3. Core Outer Core - It is very hot - The material is in liquid form Inner Core - It is under the greatest pressure - The material is in solid form Sunday, November 4, 2018 - What are plates? Plates are the broken pieces of the lithosphere and they can be also called as tectonic plates. Plates Shape They vary in shape Thickness and sizes They have diﬀerent thickness and sizes The Direction of Movement They move in diﬀerent directions The Kind of Crust they carry Some carry both oceanic and continent crust. Some carries oceanic crust only. - Why do plates move? Ridge Push (1) 1.The intense heat in the Earth’s core causes some rocks to melt. This molten rock is called the magma. 2. It rises towards the Earth’s surface. 3. When the rising magma reaches the lithosphere, it creates a fissure. 4. The upwelling hot magma will fill the fissure and form new crustal materials. 5. These materials are hot and have low densities. They rise above the existing crust, forming an up-swelling ridge. 6. When the materials are cool off, it solidifies and becomes a new part of the oceanic lithosphere. 7. As the new lithosphere cools off, its density increases and slides down from the two sides of the ridge 8. This action pushes the rest of the plates away, calling the ridge push. Sunday, November 4, 2018 Slab Pull (2) 1. As the newly formed part of the oceanic lithosphere continues to move away from the ridge, it merges with some of the rock materials in the asthenosphere and gets thicker. 2. After millions of years, they become a heavy, dense slab plate. 3. When this plate collides with other plates, it sinks into the asthenosphere as it is heavier. 4.This creates a suction force that pulls the rest of the plate behind it, called the slab pull. - What types of plate boundaries are there? Convergent, Divergent and Transform. Type of Plate Boundary Divergent Plate Boundary Convergent Plate Boundary Transform Plate Boundary Movement of Plates Plates divergent or move apart Plates converge or move towards each other Slides past each other Eﬀects on the Lithosphere New Crustal Materials are formed The denser plate sinks into the asthenosphere. No crustal materials is formed or subducts. Sunday, November 4, 2018 Distribution of Plate Boundaries GEOGRAPHY UNIT 1-3 - Three types of internal forces Three Types of Forces: Compressional Force, Tensional Force, Shearing Force Types of internal processes in compressional force: Folding, Faulting, Volcanism Types of internal processes in tensional force : Faulting, Volcanism Types of internal processes in shearing force: Faulting These forces give rise to three internal processes: Folding, Faulting and Volcanism. Sunday, November 4, 2018 - What is Folding? Folding is the process by rock layers which are folded up under compressional force. Landforms/features formed by folding: Fold and Fold Mountains, for example: The Himalayas, The Alps, The Rockies, The Andes. - What is Faulting? Faulting is the process where rocks are broken and displaced relative to each other. During the process of faulting, rocks are displaced along cracks and fractures. These cracks and fractures along which rocks move are called faults. Under Tensional Force, the rock block on the right moves down. The fault formed is called the Normal Fault. Under Compressional Force, the rock block on the right slides past each other. The fault formed is called the Reverse Fault. Under Shearing force, the rock block on the right slides past each other. The fault formed is called the Strike-Slip Fault. Sunday, November 4, 2018 Landforms/Features formed by faulting: Block Mountains (Horst) : The upthrown block of land formed between two faults. It has a flattopped highland surrounded by steep fault scraps on two sides. Rift Valleys (Grabens) : A downthrown block bounded by two faults. It has a flat-bottomed valley with a steep fault scrap on each side. What is volcanism? Volcanism refers to all the process related to the occurrence and movement of magma. Magma escapes from the magma chamber and reaches the earth’s surface, then magma becomes lava. The above process is called extrusive volcanism. After that, magma cools and solidifies before reaching the Earth’s surface, and this process is called intrusive volcanism. Landforms/ Features formed by volcanism: Sunday, November 4, 2018 GEOGRAPHY UNIT 1-4 - The major landforms found at divergent plate boundaries? At divergent plate boundaries, Ridge Push, Tensional Force, Faulting and Volcanism is found. In divergent plate boundaries, mid-oceanic ridge, rift valleys and transform fault are also found. 1. Along the divergent plate boundaries, the South American Plate and the African Plate split from each other and a fissure is created. 2. Hot magma rises through the lithosphere and fills the fissure. The hot lava cools and solidifies. This creates new crustal materials. 3. Newly formed crustal materials are hot and have a low density. They rise above the existing crust and form a mid-oceanic ridge on the seabed. 4. Ridge push causes the plates to move apart. Under Tensional force, normal faults occurs. 5. As plates keeps on moving apart, the central block of the ridge sinks to form a ridge valley. 6. On the other hand, the mid-oceanic ridge is not a continuous ridge, but is broken into lots of many small segments. Each segment is connected by a fault, called a transform fault. In divergent plate boundaries, submarine volcanoes and volcanic islands are also formed. 1. Cracks form in the plates under tensional force. 2. When magma rises through these cracks, volcanism occurs. Sunday, November 4, 2018 3. Active submarine volcanoes form. 4. Repeated eruptions raise the height of the submarine volcanoes. 5. When they rise above the sea level, volcanic islands are formed. - The major landforms found at convergent plate boundaries? At convergent plate boundaries, slab pull, shearing force and faulting is found. 1. Ocean-Continent Collision I. When the Nazca Plate and the South American Plate collide, the denser Nazca Plate subducts under the South American Plate. II. This produces a deep and elongated trough called an ocean-trench (v-shaped), which is Peru-Chile Trench. III. At the same time, sediment from the South American landmass is washed down deposited in the coastal water. Later, the layers of sediments are subjected into sedimentary rocks. IV. When the two platers collide, the sedimentary rock is folded up under compressional force. Fold Mountain, which is the Andes is formed. V. During Subduction, water is released from the subjected plate and it causes the asthenosphere to melt as a lower temperature, this forms magma. ( Heat and Water form Magma) VI. At the same time, folding and subduction caused by compressional force produces cracks in the rocks. VII. When magma rises through cracks, volcanic eruption occurs, this forms volcanoes as Mount Chimborazo on the mountain belt. Sunday, November 4, 2018 2. Ocean-Ocean Continent.