How do s and p waves move through the earth? what happens to them as they move through the layers?
S and P waves are seismic waves that are generated during earthquakes and can also be generated by other sources such as explosions. These waves move through the Earth in different ways.
1. S waves (Secondary or Shear waves):
S waves are transverse waves, meaning that they cause particles to vibrate perpendicular to the wave's direction of travel. As S waves propagate through the Earth, they move in a shearing motion similar to waves moving through a rope. They are slower than P waves and cannot travel through liquids or gases, only through solid materials.
When S waves encounter different layers within the Earth, the following happens:
- In the Earth's outer core, which is a liquid layer, S waves cannot propagate and are completely absorbed. This is known as S-wave shadow zone.
- In the Earth's mantle, which is a solid layer, S waves can propagate, but they change direction and experience a decrease in velocity due to differences in density and composition.
- In the Earth's crust, S waves can propagate with minor changes depending on the specific properties of the crustal rocks.
2. P waves (Primary or Pressure waves):
P waves are compressional waves, meaning that they cause particles to vibrate parallel to the wave's direction of travel. These waves are faster than S waves and can travel through solids, liquids, and gases.
As P waves propagate through the Earth, the following happens:
- In the Earth's outer core, P waves can propagate but experience a slight change in velocity due to different density and composition compared to the mantle.
- In the Earth's mantle, P waves can propagate with minor changes in velocity due to variations in density and composition of the rock material.
- In the Earth's crust, P waves can propagate with minor changes depending on the specific properties of the crustal rocks.
In summary, S waves cannot travel through the Earth's liquid outer core, and both S and P waves experience changes in velocity and direction as they pass through different layers of the Earth due to variations in density and composition.
S waves, also known as secondary waves, and P waves, also known as primary waves, are two types of seismic waves that move through the Earth during an earthquake. Here's how they move through the Earth's layers:
1. P Waves (Primary Waves):
- P waves are the fastest seismic waves and can travel through solids, liquids, and gases.
- As P waves move through the Earth, they compress and expand the material in the same direction as their wave propagation (parallel to the wavefront).
- P waves can travel through both the Earth's outer core and inner core.
- However, P waves experience a slight change in direction and speed as they pass from one layer to another due to the change in density and rigidity of the material.
2. S Waves (Secondary Waves):
- S waves are slower than P waves and can only travel through solid materials.
- As S waves move through the Earth, they cause the material to move perpendicular to their wave propagation (perpendicular to the wavefront).
- When S waves encounter the liquid outer core, they cannot pass through it, leading to the creation of a shadow zone on the opposite side of the Earth where S waves are not detected.
As seismic waves move through the layers of the Earth, their speed, direction, and behavior may be affected due to the varying properties of the materials they encounter. For example:
- When seismic waves cross the boundary from the mantle to the core, they experience a significant change in density and composition, resulting in a change in direction and speed.
- The liquid outer core does not support the propagation of S waves, causing them to be entirely absorbed or reflected in this layer.
- The waves may also be refracted or bent when passing through regions of varying properties.
Overall, the movement and behavior of seismic waves in the Earth's layers provide valuable information about the internal structure and composition of our planet.
S and P waves are types of seismic waves that propagate or move through the Earth's interior during an earthquake. Here's an explanation of how these waves move through the Earth and what happens to them as they pass through its different layers:
1. S (Shear) Waves:
S-waves are transverse waves that move by displacing particles perpendicular to the direction of wave propagation. As they travel through the Earth, they pass through various layers, including the crust, mantle, and core. Here's what happens to S-waves in each layer:
- Crust: S-waves can travel through the crust, but their speed and intensity may vary depending on the type of rocks present. In general, they propagate relatively slowly through solid, rigid rocks.
- Mantle: In the uppermost part of the mantle, S-waves can pass through and maintain their transverse motion. However, as they reach the lower mantle, they encounter a boundary called the "Gutenberg Discontinuity." At this point, S-waves suddenly disappear because the lower mantle is believed to be partially molten.
- Core: S-waves cannot propagate through the Earth's liquid outer core. This is because liquids, such as the molten iron present in the outer core, do not possess shear strength and cannot transmit transverse motions. So, S-waves are completely absorbed or "shadowed" by the outer core.
2. P (Primary) Waves:
P-waves are longitudinal or compressional waves that push and pull the particles in the same direction as the wave's motion. Here's what happens to P-waves as they travel through the Earth's layers:
- Crust: P-waves can propagate through the crust relatively easily, both in solid and partially molten rocks, as they compress and expand the material.
- Mantle: As P-waves move through the uppermost part of the mantle, they experience a change in velocity due to the differences in rock composition and density. This change in velocity results in a phenomenon called "refraction," causing the P-wave path to bend. The same refraction phenomenon occurs again as P-waves cross into the core.
- Core: P-waves can propagate through the Earth's liquid outer core, but their speed decreases and their direction changes due to refraction. When P-waves reach the boundary of the solid inner core, they abruptly speed up again.
In summary, S-waves can travel through the Earth's crust and uppermost mantle but disappear in the lower mantle and are completely absorbed by the liquid outer core. P-waves, on the other hand, can propagate through solid and liquid regions but experience changes in speed and direction as they encounter various layers and boundaries within the Earth.