U1- Restless Earth Flashcards
Describe the core.
The core is the hottest part, at 4000-5000°C.
It is made of iron/nickel and is split between the inner core and the outer core.
The inner core is very dense solid. The outer core is very dense liquid.
Describe the mantle and crust.
The upper mantle is partially molten whilst the main mantle is solid.
The crust is very thin compared to the mantle (8-65km) and core and is divided between oceanic crust and continental crust.
Oceanic crust is heavier than continental crust because it is made of basalt whilst continental crust is made of granite.
Why do the Earth’s plate tectonics move?
High temperatures in the core caused by radioactive decay causes convection currents. These cool and spread out as they rise before sinking again. The movement can move the tectonic plates.
What is a constructive plate margin?
Constructive margins are formed by riding magma splitting up continental crust and forming new oceans. This is happening in East Africa today in its continental rift zone.
What is a destructive plate margin?
In some places oceanic plated collide with continental plates.
When this occurs, the denser oceanic plate sinks beneath the continental plate. This process is known as subduction. As the oceanic plate is subducted into the mantle it is subjected to creased pressure and temperature. These conditions cause some lightweight materials to melt and rise to the surface to form volcanoes.
The collision of the plates also lifts and buckles the continental plates, creating fold mountains for example the Andes.
What is a conservative plate margin?
Where plates slide past each other or move in the same direction but at different speeds great strain builds up along the junction, with sudden lurches along the fault. Earthquakes are frequent and often large.
A well known example is along the west coast of the USA, especially the San Andreas fault.
Describe a composite volcano
Composite/strato volcanoes are steep sided and formed from alternating layers of ash and lava.
The lava is vicious and flows slowly and often ‘freezes’ in the central vent. This means pressure builds up over time.
Eruptions are infrequent and sometimes unpredictable, but are much more dangerous to any human populations nearby.
Example: Mt Sakurajima (Japan)
Describe a shield volcano.
A shield volcano has gentle slopes, covers a large area and is formed from almost all lava.
Lava is fluid so it flows quickly from many fissures.
Eruptions are very frequent but generally gentle.
Example: Mauna Loa (Hawaii)
Evaluate how hazardous volcanic eruptions and earthquakes are.
Volcanic eruptions do not generally kill many people because volcanoes are mountains and tend not to be located in desirable locations.
Many earthquake regions are densely populated and earthquake events cannot be predicted so are more dangerous than volcanoes.
Both large volcanic eruptions and earthquakes can cause a tsunami as a secondary hazard.
Name some factors which control the severity of earthquakes.
- Magnitude of earthquake on Richter scale.
- Distance from epicentre.
- Depth of earthquake (shallow earthquakes are more destructive).
- Time of day.
- Level of preparedness and quality of emergency services.
What are primary and secondary impacts?
Primary impacts are the immediate effect of an earthquake on property and people.
Secondary impacts are the impact on property and people of an event after it has finished.
For a named earthquake in a developed country, explain its primary and secondary impacts.
In New Zealand in 2010, an earthquake at 7.1 magnitude with 10km depth struck at 4:30am.
Primary- no deaths, 100 injuries. Damage to property £1.8 billion. Deaths were so low because most people were asleep and the buildings had strong structures.
Secondary- major aftershock at 6.3 magnitude killed 185 people in 2011.
For a named earthquake in a developing country, explain its primary and secondary impacts.
In Haiti in 2010 an earthquake at 7.0 magnitude with depth 13km struck at 5pm.
Primary- 316,000 deaths and 300,000 injured. Economic losses of £8.5 billion. Poverty and slums made people more vulnerable to building collapse.
Secondary- 7,000 killed. Estimated 1 million people homeless and cholera spread due to lack of clean water and sanitation.
Using an example of a volcanic eruption, describe its impact on people and the economy.
Mount Merapi in Indonesia is a composite volcano which erupted in 2010.
Primary social- 360,000 evacuated, 850 killed or injured.
Primary economic- several villages and farm crop destroyed, flights in area were cancelled.
Secondary social- area 10km declared danger zone. Thousands spent weeks in cramped emergency centres.
Secondary economic- $600 million economic losses due to reduced farming and lost tourism income.
How can volcanic eruptions and tsunamis be predicted?
Gas emissions, earth tremors and ‘bulging’ on the volcano can be measured and used to predict eruptions.
Tsunami warning sirens can be used to evacuate people from coasts before tsunami waves strike.
Name the 13 main tectonic plates.
