Quick Review Flashcards - Click to flip and test your knowledge!
Question
What is the geographical definition of an earthquake?
Answer
A tremor below the surface of the earth which causes shaking of the crust.
Question
Approximately how many earthquakes are recorded globally each year according to scientists?
Answer
20,000.
Question
What is the primary physical cause of earthquakes in the earth's crust?
Answer
Strain.
Question
Earthquakes occur when the crust is unable to accommodate strain, resulting in a sudden release of energy as _____ waves.
Answer
Seismic.
Question
In the context of volcanic causes, what substance is pushed upward to violently push the earth's crust?
Answer
Hot gases.
Question
The 1883 volcanic eruption of _____ between the islands of Sumatra and Java caused a severe earthquake and tsunami.
Answer
Krakatoa.
Question
According to the plate tectonic theory, most earthquakes occur on account of _____.
Answer
Plate movements.
Question
The 'Pacific Ring of Fire' is a high-risk region for tectonic earthquakes located in which part of the world?
Answer
South East Asia and the edges of the Pacific Ocean.
Question
The 2001 Bhuj earthquake in Gujarat was caused by the lowering of the Indian plate below the _____ plate.
Answer
Asiatic.
Question
What geological process involves the internal displacement of rocks due to compressional and tensional forces?
Answer
Folding and Faulting.
Question
In 1906, which famous fault in California slipped along a segment of 430 km, causing a major earthquake?
Answer
San Andreas Fault.
Question
How can the construction of huge dams, such as the Koyna dam in Maharashtra, cause earthquakes?
Answer
By creating man-made pressure near seismically active fault zones.
Question
Which human activities in Colorado during the 1960s were identified as causes for several earthquakes?
Answer
Chemical waste dumping and underground explosions.
Question
Seismic waves that are compressional and behave similarly to sound waves are known as _____ waves.
Answer
P (Primary or push).
Question
Which state of matter can P-waves pass through as they travel through the earth?
Answer
Solids, liquids, and gases.
Question
Which seismic waves are distortional and vibrate at right angles to the direction of wave movement?
Answer
S (Secondary or shear) waves.
Question
Why are S-waves unable to travel through the earth's core?
Answer
They cannot be transmitted by liquids.
Question
Which seismic waves travel along the surface of the earth and are recorded last on a seismogram?
Answer
L (Surface or long) waves.
Question
What are the two specific types of identified L-waves?
Answer
Love waves and Rayleigh waves.
Question
The point of origin of seismic waves within the earth's interior is called the _____.
Answer
Seismic focus.
Question
The point on the earth's surface directly above the seismic focus is the _____.
Answer
Epicentre.
Question
What is the typical depth range for the seismic focus of most earthquakes?
Answer
8 to 35 km.
Question
Which instrument uses a vibrating pen and a travelling strip of paper to record seismic waves?
Answer
Seismograph.
Question
How does a seismograph calculate the distance between the recording station and the epicentre?
Answer
By measuring the time interval between the arrival of P and S waves.
Question
What does the Richter scale measure with mathematical precision?
Answer
The magnitude (amount of energy released) of an earthquake.
Question
What is the numerical range of the Richter scale?
Answer
1 to 9.
Question
On the Richter scale, each whole number increase represents a _____-fold increase in the amplitude of shock waves.
Answer
10.
Question
Which scale grades earthquakes on a 12-point scale based on observed effects and damage?
Answer
The Mercalli scale.
Question
What was the magnitude of the 1897 Assam earthquake in India?
Answer
8.7.
Question
The Nepal earthquake of 25 April 2015 measured _____ on the Richter scale.
Answer
7.8.
Question
Geologically, earthquakes are considered part of _____ forces and regarded as constructive movements.
Answer
Endogenic.
Question
How does the constructive effect of energy release during earthquakes benefit the Earth?
Answer
It helps keep the earth in good shape.
Question
Which Japanese bay was uplifted by 200 metres in 1923 due to an earthquake?
Answer
Sagami Bay.
Question
In the Himalayan region, how do earthquakes constructively contribute to the landscape?
Answer
By triggering landslides that lead to the formation of lakes.
Question
What destructive effect caused the ancient city of Dwarka in Gujarat to be located under the sea today?
Answer
Submergence.
Question
How do earthquakes render land unsuitable for agriculture in terms of water resources?
Answer
By changing the course of rivers.
Question
Earthquake shock waves in mountain ranges like the Alps and Andes often lead to which dangerous secondary phenomenon?
Answer
Landslides.
Question
Why do fires frequently break out in townships during earthquakes?
Answer
Inflammable materials, broken gas pipes, and live electric wires.
Question
The term 'Tsunami' comes from Japanese words meaning _____.
Answer
Harbour waves.
Question
Where do tsunamis occur most frequently in the world?
Answer
The Pacific Ocean.
Question
Approximately how many people were killed by the December 2004 Indian Ocean tsunami?
Answer
275,000.
Question
How do earthquakes cause flash floods?
Answer
By damaging dams and embankments or by creating debris that diverts river flow.
Question
Which earthquake belt accounts for 70% of all recorded earthquakes globally?
Answer
The Circum-Pacific Mountain Belt.
Question
The Mid-world Mountain Belt, which includes the Alpine-Himalayan ranges, accounts for _____% of global earthquakes.
Answer
20.
Question
Which earthquake belt is located along mid-oceanic ridges and accounts for 10% of global earthquakes?
Answer
The Mid-Atlantic Ridge.
Question
In the Mid-Atlantic Ridge belt, why do earthquakes occur along the ridges?
Answer
Tectonic plates move in opposite directions.
Question
Which group of scientists was the first to discover the use of P and S waves for earthquake prediction in the 1960s?
Answer
The Russians.
Question
What scientific methods do the Japanese use to attempt earthquake prediction?
Answer
Measuring changes in sea level and variations in Earth's magnetic field.
Question
Term: Fold
Answer
Definition: A bend in layered rocks in the crust, most commonly found in sedimentary rocks.
Question
Term: Fault Plane
Answer
Definition: The planar (flat) surface along which there is a slip during an earthquake.
Question
Which scale is considered the most accurate and reliable for measuring the size of very large earthquakes?
Answer
The moment magnitude ($M_w$) scale.
Question
Where and when was the highest magnitude earthquake ($M_w$ 9.5) ever recorded?
Answer
Valdivia, Chile, on 22nd May 1960.
Question
The December 2018 tsunami in Java and Sumatra was likely caused by undersea landslides from the eruption of which volcano?
Answer
Anak Krakatau.
Question
What is the difference between a fold and a fault in the earth's crust?
Answer
A fold is a bend in layered rocks, while a fault is a fracture with relative movement between crust blocks.
Question
Which type of seismic wave is specifically described as being 'distortional'?
Answer
S (Secondary or shear) waves.