Context: An earthquake is caused when tectonic plates shift. But quakes themselves aren’t restricted to the earth. For example, small tremors have also been detected on the moon.
- It seismic tremors or vibrations that occur on the Moon’s surface.
- It is less intense than earthquakes on Earth. The strongest moonquakes can reach magnitudes of up to 5.5 on the Richter scale, but most are much weaker.
- It is measured using seismometers placed on the Moon’s surface by Apollo missions. These instruments recorded data from 1969 to 1977.
- Between 1972 and 1977, 28 shallow moonquakes were observed.
- It has helped scientists learn about the Moon’s internal structure, composition, and history.
Causes and types of moonquakes:
- Tidal forces: Gravitational interactions between the Moon and Earth can cause stress and strain on the Moon’s surface, leading to moonquakes, known as deep moonquakes (~700 km below the surface).
- Meteorite impacts: Craters on the moon can also form when meteors hit its surface, and since the moon doesn’t have an atmosphere, even small impacts can make big craters. There are thousands of these craters on the moon’s surface.
- Thermal stress: The moon gets very hot and very cold, with temperatures ranging from 121 degrees Celsius to -133 degrees Celsius, a difference of 250 degrees Celsius,the expansion and contraction of the lunar surface can induce moonquakes.
- Volcanic activity: Movement of magma or the collapse of lunar lava tubes.
The first three kinds of moonquakes mentioned above tend to be mild; however, shallow moonquakes caused by volcanic activity can register up to mB=5.5 on the body-wave magnitude scale.