2.1 Earthquakes And Volcanos Flashcards
Earthquake:
A sudden movement of the Earth’s crust
Focus:
The position within the Earth where an earthquake occur.
Epicentre:
The point on the Earth’s surface directly above the focus of an earthquake. The earthquake has more strength the nearer to it.
Richter Scale:
It’s a scale that measures the magnitude/strength of earthquakes using a seismometer, and is shown on a seismograph
Mercalli Scale:
The Mercalli Scale describes the intensity of an earthquake based on its observed effects
Structure of the Earth:
- The Earth is made up of 4 main layers: Inner core , outer core , mantle , and crust
- There is a very high pressure in the inner core and it’s very dense
Constructive plate boundary
- between oceanic and oceanic plate
- two plates move apart from each other
- magma from the mantle rises to fill the gap, creating land
- in this process new oceanic crust is formed , creating mid ocean ridges
-> e.g. mid Atlantic ridge
Destructive plate boundary
- oceanic and continental
- oceanic plate subducts because continental is denser
- much friction (causes heat) so oceanic plate melts
- Bea comes excess magma in the mantle , builds up pressure and erupts as an explosive volcano
-> earthquakes also occur due to the friction and tension between the two plates
Collision plate boundary
- two continental plates move towards each other
- as they have the same density, they push each other up into fold mountains
- earthquakes occur due to friction and tension
Conservative plate boundary
- two plates slide past each other
- land is neither created nor destroyed
- earthquakes occur due to the friction and tension between the two sliding plates that catch on each other
Earthquakes primary hazards:
Ground shaking
- At the Earth’s surface, earthquakes shake and displace the ground
- This might destroy infrastructures and transportations
- destroy people’s homes -> left homeless
Secondary earthquake hazards
Tsunami
If the focus of the earthquake is beneath the sea, a tsunami can occur due to the displacement of water
How to reduce impacts of earthquakes
- Build more seismic (earthquake-proof) buildings
- Educate people
- Have better forecasting technology to predict earthquakes - by measuring crustal movement and noting strange animal behaviours
- Avoid living in certain areas - e.g. areas with weak rocks, faulted rocks, and soft soils
- Build safe houses
Where are chains of volcanos found
There are chains of volcanoes located at an isolated hotspot
Shield volcanoes:
- A gentle, low-angled volcano formed of runny lava.
- The lava is capable of flowing long distances before cooling
- found at constructive plate boundaries
Composite volcanos:
- found in destructive plate boundaries
- steep + explosive volcano with viscous lava
- have layers of ash and lava
-> lava te do to dry fast
Chamber:
The reservoir of magma located deep inside a volcano
Crater:
Depression at the top of a volcano following a volcanic eruption.
Vent:
The channel through which volcanic material is ejected
Active volcanoes:
A volcano currently showing signs of activity
Dormant volcanoes:
A volcano that has not erupted for a very long time but could erupt again
Extinct volcanoes:
A volcano that has shown no signs of volcanic activity in historic times
Volcano hazards
- Very hot cloud of hot rock and ash might stay in the atmosphere for months and might cover nearby land with ash
-> This can block the sun and cause local climate change
-> This can also affect flights - SO2 is released from the volcano, The SO2 can react with water vapour in the
atmosphere to cause acid rain
-> This can damage buildings
-> acidify soil - If a volcano collapses onto the sea this causes a sudden movement of water in the ocean causing a tsunami
- might destroy houses and infrastructure. This means there might be a lack of food and hygiene in that area, so diseases are more likely to spread
Opportunities living near volcanos:
- People might be too poor to move or have nowhere else to live
- People might have families living by a volcano, and they prefer to stay together with their family
- Volcanic environments can be good locations for farming as volcanic soils are very fertile
- Minerals deposits, for example silver and diamonds, are found near volcanoes
- Geothermal energy can be harnessed, which provides cheaper electricity
-cheaper land - beautiful landscapes
- people who want to study volcanoes
Reducing impacts of volcanoes
- Predict volcanic eruption by using monitoring equipment such as seismometers
- Spraying lava flows with water.
- Dig lava diversion channels to divert lava flows away from towns
