Earthquakes and Seismic Activity

Earthquakes

• Earthquakes are not unique to Earth; scientists have measured quakes on the Moon, Mars, Venus, and several moons of Jupiter.
• Earthquakes occur when there is a sudden movement of the Earth's crust at a fault line.
• The location where an earthquake begins is called the epicenter.
• The epicenter is where the most intense shaking is often felt, but the vibrations from an earthquake can still be felt and detected hundreds or thousands of miles away.

Seismic Waves and Seismometers

• Seismic waves are vibrations that travel through the Earth.
• Scientists can measure seismic waves using instruments called seismometers.
• A seismometer detects seismic waves below the instrument and records them as a series of zig-zags.
• Scientists can determine the time, location, and intensity of an earthquake from the information recorded by a seismometer.

The Earth's Atmosphere

• The atmosphere is the air that surrounds the Earth, extending up to 480 km in thickness.
• 99% of the atmosphere's thickness lies up to 32 km above the Earth's surface.
• The atmosphere has a mixture of gases that sustains life on Earth.
• The major role of the atmosphere is to contain the entry of ultraviolet rays.
• The composition of the Earth's atmosphere is:
  • Nitrogen: 78%
  • Oxygen: 21%
  • Argon: 0.93%
  • Carbon dioxide: 0.04%
  • Trace amounts of neon, helium, methane, krypton, and hydrogen, as well as water vapor

Layers of the Atmosphere

• The mesosphere is the third layer of the atmosphere, extending up to 80 km in height.
• Temperature decreases with increasing altitude in the mesosphere, dropping to -100°C at 80 km.
• Meteorites burn in this layer when entering the atmosphere from outer space.
• The thermosphere is located between 80 and 400 km above the mesosphere and contains electrically charged particles called ions.
• Temperature increases with increasing height in the thermosphere.
• Radio waves transmitted from the Earth are reflected back to the Earth by the thermosphere.
• Satellites orbit in the upper part of the thermosphere.
• The exosphere is the uppermost layer of the atmosphere, gradually merging with outer space.

Earth's Layers

• The Earth is made up of four basic layers: a solid crust, a hot, nearly solid mantle, a liquid outer core, and a solid inner core.
• The lithosphere is the solid crust and top, stiff layer of the mantle.
• The lithosphere is made up of giant puzzle pieces called tectonic plates that are constantly shifting.
• Tectonic plates are responsible for earthquakes, as they cause stress on the Earth's crust, leading to cracks called faults.

Earthquakes

• Earthquakes are not unique to Earth; scientists have measured quakes on the Moon, Mars, Venus, and several moons of Jupiter.
• Earthquakes occur when there is a sudden movement of the Earth's crust at a fault line.
• The location where an earthquake begins is called the epicenter.
• The epicenter is where the most intense shaking is often felt, but the vibrations from an earthquake can still be felt and detected hundreds or thousands of miles away.

Seismic Waves and Seismometers

• Seismic waves are vibrations that travel through the Earth.
• Scientists can measure seismic waves using instruments called seismometers.
• A seismometer detects seismic waves below the instrument and records them as a series of zig-zags.
• Scientists can determine the time, location, and intensity of an earthquake from the information recorded by a seismometer.

The Earth's Atmosphere

• The atmosphere is the air that surrounds the Earth, extending up to 480 km in thickness.
• 99% of the atmosphere's thickness lies up to 32 km above the Earth's surface.
• The atmosphere has a mixture of gases that sustains life on Earth.
• The major role of the atmosphere is to contain the entry of ultraviolet rays.
• The composition of the Earth's atmosphere is:
  • Nitrogen: 78%
  • Oxygen: 21%
  • Argon: 0.93%
  • Carbon dioxide: 0.04%
  • Trace amounts of neon, helium, methane, krypton, and hydrogen, as well as water vapor

Layers of the Atmosphere

• The mesosphere is the third layer of the atmosphere, extending up to 80 km in height.
• Temperature decreases with increasing altitude in the mesosphere, dropping to -100°C at 80 km.
• Meteorites burn in this layer when entering the atmosphere from outer space.
• The thermosphere is located between 80 and 400 km above the mesosphere and contains electrically charged particles called ions.
• Temperature increases with increasing height in the thermosphere.
• Radio waves transmitted from the Earth are reflected back to the Earth by the thermosphere.
• Satellites orbit in the upper part of the thermosphere.
• The exosphere is the uppermost layer of the atmosphere, gradually merging with outer space.

Earth's Layers

• The Earth is made up of four basic layers: a solid crust, a hot, nearly solid mantle, a liquid outer core, and a solid inner core.
• The lithosphere is the solid crust and top, stiff layer of the mantle.
• The lithosphere is made up of giant puzzle pieces called tectonic plates that are constantly shifting.
• Tectonic plates are responsible for earthquakes, as they cause stress on the Earth's crust, leading to cracks called faults.

Learn about earthquakes and seismic activity, including how they occur on Earth and other planets. Discover the composition of the atmosphere and more.