Prediction and monitoring of seismic and volcanic events Flashcards Preview

A Level Geography - Plate tectonics and associated hazards > Prediction and monitoring of seismic and volcanic events > Flashcards

Flashcards in Prediction and monitoring of seismic and volcanic events Deck (17):

Are humans able to predict seismic and volcanic events?

Not accurately.
Large scale monitoring of tectonic activity - narrows down locations/time frames.


How are volcanoes monitored?

Earthquake monitoring.
Monitoring gas emission.
Ground deformation.
Thermal monitoring.
Satellite images and remote sensing.
Mass movements and failures.


How does earthquake monitoring help predict volcanic events?

Seismic waves show if a volcano is getting ready to erupt.
Increasing intensity in frequency/size before eruption.
Types of earthquakes that occur and start/end are also key signs.
Monitored through seismographs.


What are the 3 different types of earthquakes before a volcanic eruption?

Short-period earthquake.
Long-period earthquake.
Harmonic tremors.


What are short-period earthquakes?

Short-period earthquakes are like normal fault-generated earthquakes.
They are caused by the fracturing of brittle rock as magma forces its way upward.


What are long-period earthquakes?

Indicate increased gas pressure in a volcano's plumbing system.


What are harmonic tremors?

Magma pushing against the overlying rock below the surface.
Strong enough to be felt as humming by people/animals.
E.g. Mount Pinatubo 1991.


How does monitoring gas emissions help predict volcanic events?

Magma rises into magma chambers - gases escape.
Sulphur dioxide increases - could signal eruption.
E.g. Pinatubo sulphur dioxide increased x10 in 2 weeks.
Directly before eruptions gas levels then drop rapidly.
Due to the sealing of gas passages by hardened magma. Increases pressure - leads to explosive eruptions.


How does ground deformation help predict volcanic events?

Magma movement within the lithosphere - ground deformation.
Volcanic swelling - magma has collected near surface.
Scientists measure slope tilt and track changes.
E.g. Mount St Helen 1980 showed this.


How does thermal monitoring help predict volcanic events?

Magma movement, changes in gas release and hydrothermal activity - thermal emissivity changes.


How does satellite images and remote sensing help predict volcanic events?

Remote sensing - satellites use.
Useful for monitoring volcanic surface changes.
Can check for upwelling magma/escaping Sulphur dioxide using gas sensing.
Ground deformation - before/after ground images.
Can measure distance between satellite/ground.


How do mass movements and mass failures help predict volcanic events?

Monitoring mass movements and failures landslides, rock falls, pyroclastic flows, and lahars.
Past activity.
Can suggest if upswelling magma is deforming the land above.


What 4 things are used to predict seismic events?

Randon gas.
Animal behavior.
Tilt meters.


How do foreshocks help predict seismic events?

Often small earthquakes before “the big one”.
E.g. Japan Tsunami (mag 9.0) was followed by a massive magnitude 7.2 earthquake.
Problem is spotting which earthquakes are foreshock warnings - many thousands of earthquakes a year.


How does Radon gas help predict seismic events?

Radon (radioactive) gas - outgassed prior earthquake.
But discounted by many seismologists.


How does animal behaviour help predict seismic events?

Animals react to an earthquake before the event/human beings.
Harmonic tremors.


How do tilt meters help predict seismic events?

Tilt meters - shows ground deformation.
Replaced by more modern satellite imagery.