CHAPTER 1 LIVING WITH TECTONIC HAZARDS Risk or Opportunity?

In this Chapter, you will explore three key questions: 1.Why are some areas more prone to tectonic hazards? 2.What landforms and associated tectonic phenomena are found at plate boundaries? 3.How do people prepare for and respond to earthquakes? CHAPTER 1 LIVING WITH TECTONIC HAZARDS

Gateway 2: What landforms and associated tectonic phenomena are found at plate boundaries? The sea started to recede. I remember learning in a geography lesson that this happens before a tsunami. I shouted to tell everyone a tsunami was coming and for them to run! Quoted from a survivor of the tsunami that took place at Mai Khao Beach, Thailand on 26 December 2004.

In December 2004, The Tsunami swamps Phuket's Chedi resort (AFP/Joanne Davis) Gateway 2: What landforms and associated tectonic phenomena are found at plate boundaries?

After the tsunami, authorities have now installed signs along this coastline. What symbols and words would you expect to see on these signs. Sketch the signs you expect to see at the beach. Explain why you thought the signs are important.

CHAPTER 1 LIVING WITH TECTONIC HAZARDS Gateway 2: What landforms and associated tectonic phenomena are found at plate boundaries? a.Why are different landforms found at different plate boundaries and how are they formed? b.What phenomena are found at plate boundaries and how are they formed?

a. Why are different landforms found at different plate boundaries and how are they formed? The movement of plates at different plate boundaries can result in various landforms such as: - Fold mountains - Rift valleys and block mountains - Volcanoes

Fold mountains Over millions of years, the folding of rocks creates a landform called fold mountains. The Himalayas, the Rocky Mountains and the Andes are examples of fold mountains.

Fold mountains are formed along convergent plate boundaries. The compressional force causes the layers of rocks to buckle and fold. This process is known as folding. Fold mountains

The upfold is called the anticline and The downfold is the syncline. When there is increasing compressional force on one limb of a fold, the rocks may buckle until a fracture forms. The limb may then move forward to ride over the other limb Fold mountains

The Himalayas Peak : Mount Everest (between Nepal and Tibet) Elevation : 8,848 metres

Fold mountains are located along convergent plate boundaries Fold mountains

Rift valleys and block mountains Rift valleys and block mountains are formed at divergent plate boundaries.

A fault is a fracture in the rocks along which the rocks are displaced. The tensional forces result in parts of the crust being fractured. This process is called faulting. Rift valleys and block mountains

A rift valley is a valley with steep sides formed along fault lines. E.g. East African Rift Valley Rift valleys and block mountains

A block mountain is a block of land with steep sides. It is formed when sections of the crust extend along fault lines and rock masses surrounding a central block sink due to tensional forces. Rift valleys and block mountains

The East African Rift Valley Is formed from the Nubian section of the African Plate and the Somalian section of the African Plate pulling away from one another.

Distribution of rift valleys and block mountains Rift valleys and block mountains

Volcanoes A volcano is a landform formed by magma ejected from the mantle onto the earth’s surface. Mount Saint Helens volcano before and after an eruption in May 1980

Magma is molten rock found below the earth’s surface. Parts of a Volcano - magma chamber - vents Magma that is ejected onto the surface is known as lava. Volcanoes

Formation, structure of, and features of a volcano

Shapes and sizes of volcanoes Volcanoes vary in shapes and sizes due to the characteristics of the lava. Viscosity refers to the stickiness of the lava The most common types of volcanoes are: - Shield volcanoes; and - Stratovolcanoes Volcanoes

Shield volcanoes Shield volcanoes have gently sloping sides and a broad summit E.g. Mount Washington, United States of America Volcanoes

Stratovolcanoes Stratovolcanoes develop from successive eruptions of lava and ash. E.g. Mount Mayon, Philippines Volcanoes

Distribution of earth’s major active volcanoes

An earthquake is a vibration in the earth’s crust caused by the sudden release of stored energy in the rocks found along fault lines. b. What phenomena are found at plate boundaries and how are they formed?

Extent of earthquakes - The Richter Scale is used to measure the magnitude of an earthquake Earthquakes

Apart from its magnitude, the extent of damage caused by an earthquake may vary based on other factors: -Population density -time of occurrence -level of preparedness -distance from the epicentre -type of soil Earthquakes

The distribution of the earth’s major earthquakes Earthquakes

Measuring earthquakes - A seismograph records the seismic waves released by an earthquake. Earthquakes

Hazards associated with living in earthquakes zones -Threat of tsunamis -Disruption of services -Fires -Landslides -Destruction of properties -Destruction of infrastructure - Loss of lives Earthquakes

Threat of tsunamis Tsunami refers to an usually large sea wave. Tsunamis may be formed by: -The movement of the sea floor during a large earthquake at subduction zones; -An underwater volcanic eruption; -An underwater landslide; and -A landslide above sea level which causes materials to plunge into the water. Hazards associated with earthquakes

In 2004, a 9.2 magnitude triggered a tsunami with waves spreading throughout the Indian Ocean. Aceh before and after the tsunami hit the area Hazards associated with earthquakes

The spread of the tsunami waves caused by the tsunami Hazards associated with earthquakes

Disruption of services An earthquake can disrupt services such as the supply of electricity, gas and water. The earthquake in Kobe, Japan, in 1995 disrupted electricity, gas and water supplies to about a million of Kobe city’s 1.4 million residents. Hazards associated with earthquakes

Fire Earthquakes may rupture gas pipes and this can provide fuel to start fires. For example, the earthquake in Kobe, Japan, in 1995 caused extensive fires. Hazards associated with earthquakes

Landslides Landslides are rapid downslope movements of soil, rock and vegetation. Mudflows may also occur when there is heavy rainfall. Hazards associated with earthquakes

Destruction of properties Earthquakes can cause destruction to many homes. People may be without homes after the disaster. Hazards associated with earthquakes

Destruction of infrastructure Earthquakes may cause cracks to form in infrastructure such as roads and bridges. Transportation can be disrupted as it is unsafe to use the damaged roads. Hazards associated with earthquakes

Loss of lives Earthquakes and their associated hazards often threaten the lives of those living in earthquake zones. Hazards associated with earthquakes

Volcanic eruptions -Occurs on land occur on the sea floor. Active, dormant or extinct Active volcanoes refers to volcanoes which are currently erupting or are expected to erupt in the future. Dormant volcanoes are currently inactive but may erupt in the near future. Extinct volcanoes refers to volcanoes without current seismic activity b. What phenomena are found at plate boundaries and how are they formed?

Risks of living near volcanic areas Some of the risks associated with living near volcanic areas include: Destruction by volcanic materials Landslides Pollution Effects on weather Volcanic eruptions

Destruction by volcanic materials Volcanic materials can lead to widespread damage of property. Volcanic eruptions

Landslides Landslides can occur due to the structural collapse of a volcanic cone. Obstruct the flow of rivers which causes floods, block roads, and bury villages and farmlands. Volcanic eruptions

Pollution Ash particles may block sunlight, suffocate crops, and cause severe respiratory problems for people and animals. Release of gases may be harmful to people. Volcanic eruptions

Effects on weather Sulphur dioxide released from volcanic eruptions has impacts on the environment It may react with water vapour and other chemicals in the atmosphere to form sulphur- based particles. These particles reflect the sun’s energy back into space and temporarily cool the earth for periods of time. Volcanic eruptions

Benefits of living near volcanic areas Fertile volcanic soil Building materials, and precious stones and materials Tourism Geothermal energy Volcanic eruptions

Fertile volcanic soil Lava and ash from the volcanic eruptions break down to form fertile volcanic soils. Favourable to agriculture Volcanic eruptions

Precious stones and minerals, building materials Volcanic rocks can be rich in precious stones and minerals. These resources can only be from a volcanic area after millions of years. An example is diamond. Volcanic eruptions

Tourism Volcanic areas offer a variety of activities for tourists to engage in. The ruins of Pompeii, Italy, is one such example. Volcanic eruptions

Pompeii was partially destroyed and buried under 4 to 6 m (13 to 20 ft) of ash and pumice in the eruption of Mount Vesuvius in CE 79. Volcanic eruptions

Geothermal energy Geothermal energy is derived from the heat in the earth’s crust. The hot water or steam can be harnessed to produce electricity. Volcanic eruptions

CHAPTER 1 LIVING WITH TECTONIC HAZARDS Gateway 2: What landforms and associated tectonic phenomena are found at plate boundaries? a.Why are different landforms found at different plate boundaries and how are they formed? b.What phenomena are found at plate boundaries and how are they formed?