Chapter 1 Gateway 2: Rift Valley And Fold Mountains Flashcards

Question

What is an earthquake? (Definition, occur, formation, energy released)

Answer 1

DEFINITION An vibration in the earth’s crust caused by the sudden release of stored energy in the rocks along fault lines OCCUR When there is plate movement along plate boundaries FORMATION Due to friction between the moving plates, plates movements cause the slow build-up of stress on the rocks found on either side of the fault. When the rocks can no longer withstand the increasing stress, they can slip many metres, causing an earthquake ENERGY RELEASED Seismic waves

Answer 2

``` FOCUS wait EPICENTRE The point on the earth’s surface directly above the focus AFTERSHOCKS Many smaller earthquakes ```

Answer 3

1. Deep-focus earthquake | 2. Shallow-focus earthquake

Answer 4

LOCATION Occurs between 70 and 700 kilometres below the earth’s surface IMPACT Smaller impact on the land surface as vibrations or seismic waves take a longer time to reach the surface and would have lost most of their energy by then

Answer 5

LOCATION Occurs in the upper 70 kilometres of the earth’s crust IMPACT Greater impact on the land as vibrations or seismic waves reach the surface more quickly

Answer 6

DEFINITION Used to measure the magnitude of an earthquake For each increasing magnitude, the impact of the earthquake becomes 10 times greater

Answer 7

``` SHIELD Low-silica lava Low viscosity Less explosive Short Divergent plate boundaries EXP: Mount Washington in the united states of america STRATO High-silica lava High viscosity Explosive Tall EXP: Mount Pinatubo in the Philippines ```

Answer 8

1. Magnitude 2. Population density 3. Level of preparedness 4. Distance from epicentre

Answer 9

Magnitude is the amount of energy released in during an earthquake and is measured using the richter scale. For each increasing magnitude on the richter scale, the impact of the earthquake becomes 10 times greater than the previous one

Answer 10

The number of people living in the affected area is an important factor. Earthquakes in sparsely populated areas are likely to affect lesser people than in densely populated areas

Answer 11

The amount of preparation taken by the authorities and citizens makes a significant difference to the impact of an earthquake. These preparations include evacuation plans. The damage caused by an earthquake is more manageable when people are prepared for it.

Answer 12

The damage caused by an earthquake is more severe when an area is closer to the epicentre of an earthquake

Answer 13

An unusually large sea wave The movement of the sea floor during a large earthquake at the subduction zones An explosive underwater volcanic eruption A landslide above sea level which causes materials to plunge into the water Tsunamis can travel long distances and cause widespread destruction at coastal areas In 2004, a 9.2 magnitude earthquake occured in the Indian Ocean and triggered a tsunami with waves that caused damage to coastal communities in 12 countries. The most damage was experience in the low-lying coastal areas of western Sumatra, including the city of Banda Aceh. The tsunami waves were between 4 to 39 metres high, and went as far inland as 10 kilometres

Answer 14

Landslides are rapid downslope movements of soil, rock and vegetation debris from a slope. They can range from several metres to several kilometres in both length and width In 1970, an earthquake off the coast of Peru destabilised the slopes of Mount Huascaran and triggered a massive landslide. The landslide travelled at more than 160km/hr and completely flattened the city of Ranrahirba within seconds. The death toll is more than 18000 and only 200 people survived the disaster.

Answer 15

An earthquake can disrupt services such as the supply of electricity, gas and water and can potentially affect a large area. Vibrations on the ground can snap pipes and break cables which may cause the outbreak of fires. Communication services such as telephone connections may also be affected. The earthquake in Kobe, Japan in 1995 damaged pipes and transmission lines. This disrupted electricity, gas and water supplies to around a million of Kobe city’s 1.4 million residents

Answer 16

Earthquakes can cause widespread destruction to many homes. People may be without homes after the disaster and reside a temporary shelter while their homes are being rebuilt The earthquake in Tohoku, Japan in 2011 caused a tsunami which travelled up to 10 kilometres inland. Extensive structural damage resulted in hundreds of thousands of people being forced to leave their homes

Answer 17

Earthquake 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 For example, after the earthquake in kobe, japan, in 1995, many places in the city became inaccessible or difficult to reach. Japan’s total cost of repair after the earthquake in tohoku, in 2011 was US$300 billion

Answer 18

Earthquakes and their associated hazards often threaten the lives of those living in earthquake zones The earthquake in Haiti in 2010 resulted in an estimated death toll of 300000 people

Answer 19

Volcanic materials can lead to widespread damage of property. Lava has high temperatures and burns the areas it flows through. Low-silica lava moves rapidly and flows over long distances, causing damage to larger areas. A pyroclastic flow can destroy everything in its path with hot rock fragments with speeds greater than 200m/s. Inhaling hot ash and gases can result in serious injury or death. Volcanic bombs can fall in areas surrounding the volcano and cause damage to property. Landslides have the potential to obstruct the flow of rivers causing floods, blocked roads, and buried villages and farmlands The eruption of Nevado del Ruiz in the Andes Mountains of South America in 1985 released a pyroclastic flow. The mixing of pyroclasts and glacier ice along its path triggered lahars. The lahar engulfed the town of Armero and killed more than 20000 people

Answer 20

Ash particles ejected during a volcanic eruption can disrupt human activities over large distances from the volcano. Thick plumes of ash may eventually settle on the ground and block sunlight, suffocate crops, and cause severe respiratory problems for people and animals The eruption of Eyjafjallajokull in Iceland in 2010 produced extensive volcanic ash clouds containing tiny particles of abrasive glass, sand and rock. These particles posed a serious danger to aircraft engines and resulted in the closure of air space over much of Europe. The cancelled flights caused delays to 1.2 million passengers daily and cost the airline industry a total of US$1.8 billion

Answer 21

Lava and ash from volcanic eruptions break down to form fertile volcanic soils which are very favourable to agriculture The volcanic soils of Java and Bali in Indonesia support the cultivation of crops such as tea. This is the main reason why these two islands have been able to support a large rural population over many decades. Despite continuous use, the soils are more fertile than most non-volcanic areas of Indonesia

Answer 22

Volcanic rocks can be rich in precious stones and minerals. Precious stones like diamonds are formed when heated and pressurised carbon is cooled in magma pipes beneath the earth’s surface The old volcanic rocks at Kimberly in South Africa are one of the world’s richest sources of diamond

Answer 23

Volcanic areas offer a variety of activities for tourists to engage in. It is also rich in histsory and people can visit these areas to learn more about them The ruins of Pompeii, Italy, were buried by layers of ash from the nearby Mount Vesuvius when it erupted in 79 CE. The unearthed archaeological site has revealed buildings left intact. Almost 3 milion people visit the site every year.

Answer 24

When groundwater comes into contact with hot rocks beneath the surface, it heats up and erupts as hot water or steam which can be harnessed to drive turbines and produce elecricity Most of Iceland’s electricity is generated from geothermal power because of the large number of volcanoes in the country. Over 70% of homes in iceland are heated by volcanic steam

Answer 25

For shield volcano, the silica content of the lava is lower so it is less resistant to flow. The lava travels further away from the vent before solidifying to create a cone with a broad base but gentle slopes. For stratovolcano, the silica content of the lava is higher so it is more resistant to flow. The lava cannot travel far but solidfy close to the vent, creating a cone with a narrow base but steep slopes