Volcanoes and Earthquakes Flashcards
Define crater
Depression at the top of a volcano following a volcanic eruption. It may contain a lake.
What are the layers of the Earth
Inner first
Inner core (Solid)
Outer core (Liquid)
Mantle (Molten)
Crust (Solid)
What is the structure of an oceanic plate (Characteristics) (Thickness) (Density) (Main rock type)
Usually carry ocean Subducted Thin (5-10km) Very dense Mostly made up of basalt and Gabbro Newer can be created and destroyed
What is the structure of a continental plate (Characteristics) (Thickness) (Density) (Main rock type)
Usually carries land Cannot be subducted Very thick (30-50km) Not very dense Made up of mainly granite Older cannot be created or destroyed
Give a description of a collision plate margin
A collision of two continental plate boundaries. As they are bothers dense as each other, neither one subducts, otherwise the Himalayas would be made up of volcanoes. As the collision occurs, they buckle, fold and rise up to form fold mountains.
Give a description of a conservative plate margin
Conservative plate margins are called conservative as neither plate is being created or destroyed. Instead it is being conserved. As the two plates move with each other, friction and stress occur along the fault line. Because of this, earthquakes occur. This is because of the release of friction and stress after it had all built up.
Give a description of a constructive plate margin
They are called constructive as they construct new oceanic plates. Because the plates diverge, the earth’s surface is stretched and gets longer. Most constructive plate margins are bellow sea level as they are both on the oceanic crust. Magma rises and flows into the fissures.(the oceanic crust then cracks and diverges, allowing newly formed crust to form, pushed by convection currents.
Give a description of a destructive plate margin
The oceanic and continental plate combine but because the oceanic plate is much more dense, it subjects underneath the continental plate. Because of this, it starts to melt as it is nearer the mantle. This turns into magma and rises, up through the continental plate and then erupting out as a volcanic eruption.
Where are convection currents
How are they formed
What are they
They are generated from the heat of the Earth’s core in the mantle.
They are caused by the decaying of radioactive elements in the earth’s core.
They are the moments of the current within the mantle which causes the plates to love on the surface of the Earth.
Give the definition of a Volcano
It’s an opening in the earth’s crust which allows molten rock, ash, dust, and gasses to escape from under the crust through vents.
Where do volcanoes form
They occur over destructive and constructive tectonic plate margins and over “hotspots” in the Earth’s crust.
What is an active Volcano
Erupting very recently or frequently, such as Mauna Loa, Hawaii.
What is a dormant volcano
Volcanoes which have erupted in historical times but not recently, e.g. Mount Kilimanjaro
What is an extinct volcano
Volcanoes which have not erupted in historic time, e.g Edinburgh castle lies on top of an extinct volcano.
What comes out of a volcano
(Solids)
(Liquids)
(Gasses)
Solid- rocks, ash and lava bombs
Liquid- lava
Gas- Sulphur dioxide and carbon dioxide
What is a Parasitic cone
A cone shaped feature found on the side (flank) of a volcano. Formed by eruptions in the secondary vents.
What is a lava dome
`A mound of viscous, (thick lava), formed by the main vent. This lava cools in the form of a dome shape.
Define Main vent
The main passage the magma rises up
Define Secondary vent
If the crater becomes blocked, then this is the alternative
Define crater
Where the magma/lava comes out of
Define Lava
Molton rock that reaches the earth
Define Ash clouds
Ashford into clouds
Define Volcanic bombs
Solidified lava, thrown out of the volcano
Define Magma chamber
Where all the magma is stored in the mantle
Give 10 hazards of a volcano
Ash falls Pyroclastic flows Lateral blasts Mudflows (lahars) Volcanic gasses Acid rain Post eruption famine and disease Tsunami Lava flows Landslides, avalanches
What is a pyroclastic flow
A gret mass of lava being erupted from a volcano and flowing at great speed.
How are mudflows formed
By the intense rainfall on loose volcanic rock deposits
What is a Stratovolcano
Very violent eruptions
Steep sides
Thick lava
At destructive plate boundaries
What is a Shield Volcano
Low, with gently sloping sides
Usually found at constructive boundaries, rising deep from the ocean floor.
Thin, runny lava
Frequent but gentle eruptions
Give 5 advantages of volcanoes
Geothermal- The magma chamber can heat water up underground which we can then use.
Fertile soil- The ash creates really fertile soil for crops.
Tourism- Tourists come to explore the volcano
Minerals- Solidifying lava can create really valuable minerals.
What is the definition of an earthquake
Is caused by the friction or stress from the plate boundaries. For example at a conservative plate boundary, both plates slide against each other, causing earthquakes.
Where does an earthquake occur
Occur along plate margins as that is where plate boundaries meet.
What is the focus
The point in which the earthquake occurs
What is the epicentre
Directly above the focus o the surface
What are seismic waves
The wave son energy from the focus
What does the Richter scale measure
The magnitude of an earthquake.
Uses a seismograph
How high does the richter scale go
3-9.1
What does the Mercalli scale measure
How much damage is caused by an earthquake
Measured on a scale between 1-12
