Volcanoes and Earthquakes Flashcards
What is a vent?
The opening in the volcano from where the lava comes out
What is the summit?
The highest point
What is the throat?
Conduits part that ejects lava and volcanic ash
What is the conduit?
The passge in the volcano through which magma travels up
What is the sill?
A flat peice of rock which forms by hardening of magma in a crack in a volcano.
Where are the main location of volcanoes?
Most are found at the edges of tectonic plates, some lie over hotspots
Can happen at convergent (destructive) and divergent (constructive) boundaries but not transform (conservative)
How do volcanoes form?
Magma rises through cracks or weaknesses in the Earth’s crust
Pressure builds up inside the Earth
When this pressure is released, e.g. as a result of plate movement, magma explodes to the surface causing a volcanic eruption
The lava from the eruption cools to form new crust
Over time, after several eruptions, the rock builds up and a volcano forms
What are the catagories of volcanoes?
active, extinct, dormant
What is a active volcano?
Volcanoes that are erupting or have recently erupted
What is a extinct volcano?
Extinct volcanoes that those that have not erupted for thousands of years
What is a dormant volcano?
Volcanoes that have not erupted for over 20 years
What are the types of volcanoes?
Fissure volcano, Shield volcano, dome volcano, ash-cinder volcano, composite volcano, caldera volcano
What is a fissure volcano?
Fissure volcanoes are produced by eruptions that occur along elongated fissures versus at a central vent.
What is a shield volcano?
broad volcanoes with gentle slopes and are shaped somewhat like a warrior’s shield lying flat on the Earth
What is a dome volcano?
Domes form from the slow extrusion of highly-viscous silicic lava
What is a ash cinder volcano?
the type of volcano that is formed by pyroclastic fragments like volcanic ashes, solidified lava pieces, volcanic clinkers, pumice and hot gases.
What is a composite volcano?
a cone-shaped volcano built from several layers of lava, pumice, ash, and tephra
What is a caldera volcano?
a large depression formed when a volcano erupts and collapses.
What is a earthquake?
An earthquake is the shaking and vibration of the Earth’s crust
Earthquakes occur when tension is released from inside the crust
What is the focus of a earthquake?
The point inside the crust where the pressure is released.
What is a epicentre of a earthquake?
The point on the Earth’s surface above the focus
Explain the basics of the energy released by a earthquake
Earthquake energy is released in seismic waves
These waves spread out from the focus
Where are the waves felt the most and damage the most during a earthquake?
Epicentre
What are the two types of waves release from earthquakes?
P and S waves
What are the properties of P waves?
They can travel through solids and liquid and therefore can be felt on the opposite side of the earth
P-waves (P stands for primary) arrive at the detector first
They are longitudinal waves which mean the vibrations are along the same direction as the direction of travel
What are the properties of S waves?
They can only travel through solids
S-waves (S stands for secondary) arrive at the detector of a seismometer second
They are transverse waves which mean the vibrations are at right angles to the direction of travel
What are surface waves?
Surface waves are similar in nature to water waves and travel just under the Earth’s surface
They are generated when the source of the earthquake is close to the Earth’s surface
What are the two basic kinds of surface waves?
Rayleigh waves, Love waves
What are Rayleigh waves?
Travel as ripples similar to those on the surface of water
What are love waves?
Cause horizontal shearing of the ground, they usually travel slightly faster than Rayleigh waves
What is seismometer?
A seismometer detects the vibrations caused by an earthquake, it plots these vibrations on a seismograph
What is the magnitude of a earthquake measured on?
The strength, or magnitude, of an earthquake is measured using the Richter scale which measures 0-10
What is the amplitude of a seismic wave?
Theamplitudeof aseismic waveis the amount the ground moves as thewave passes by
What is triangulation used for?
Used to locate the epicentre of an earthquake
Seismograms from three locations are used
What are the steps of Triangulation?
Find the S-P time
Use a graph to find the distance from the epicentre
Using the scale on the map convert actual distance to map distance
Draw a circle on the map using the map distance as your radius and the seismograph location as the centre
Where the three circles cross is the location of the epicentre
