Earthquakes and Volcanoes Flashcards
To Revise
What is an earthquake?
An earthquake is a sudden and violent shaking of the ground, often caused by movement along faults in the Earth’s crust.
How does an earthquake occur?
An earthquake occurs due to the accumulation and sudden release of stress along faults in the Earth’s crust. This process involves tectonic plate movements, stress build-up, rupture, and the propagation of seismic waves, resulting in ground shaking.
What do you understand by the term ‘ Focus’ or ‘Hypocenter’?
The focus, or hypocenter, is the precise location beneath the Earth’s surface where seismic energy is first released during an earthquake. It marks the initial point of rupture where the accumulated stress within the Earth’s crust is released, causing the earthquake.
Where is the “Epicentre” located
The point is vertically / 90 degrees above the focus which lies within the crust where an Earthquake originates. Generally lies within a depth of 6 km in the Earths crust.
What are Seismic Waves?
Seismic waves are the waves of energy that travel through the Earth’s layers as a result of an earthquake
What does the RICHTER SCALE Measure
Magnitude of an earthquake by measuring the seismic waves. Linear and Descriptive scale.
What does the MERCALLI SCALE Measure
Measures the intensity of an earthquake based on its effects and impact on people, buildings, and the Earth’s surface. Logaritmitic.
Differentiate between ‘seismograph’ and ‘seismogram’
A seismograph, also known as a seismometer, is an instrument used to detect and record seismic waves produced by earthquakes.
A seismogram is the actual record or output produced by a seismograph. It is a graphical representation of the seismic waves detected by the seismograph.
What is a volcano?
A volcano is an opening in the Earth’s crust through which gases, molten rocks, ash, lava, stream are emitted outwards in the courseofaneruption
What is an ACTIVE VOLCANO?
A volcano which is erupting or has recently erupted. Eg. Mt. Etna
What is a DORMANT VOLCANO?
A volcano which has not erupted in a long time but which is known to be capable of erupting.
What is an EXTINCT VOLCANO?
A volcano which scientists believe will never erupt again
