Table of Contents
What happens in a shadow zone?
The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves. The shadow zone results from S waves being stopped entirely by the liquid core and P waves being bent (refracted) by the liquid core.
What happens to secondary waves when they reach the outer core?
What happens when S waves reach Earth’s outer core? S waves cannot travel through liquids, and since Earth’s core is liquid, S waves do not travel directly through Earth. P waves can travel through a liquid and solid, but can be reflected off of the “surface” layer.
Where does the secondary waves can travel?
Secondary waves S-waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses. S-waves are slower than P-waves, and speeds are typically around 60% of that of P-waves in any given material.
What is the predicted shadow zone for secondary waves that do not travel through a liquid?
The secondary seismic waves cannot pass through the liquid outer core and are not detected more than 104° (approximately 11,570 km or 7,190 mi) from the epicenter.
What happens to S waves when they reach the outer core and what does this indicate about this layer?
S waves cannot pass through the liquid outer core, but P waves can. The waves are refracted as they travel through the Earth due to a change in density of the medium. This causes the waves to travel in curved paths.
Why do secondary waves disappear?
Data from many earthquakes has shown that S-waves disappear when they encounter the liquid outer core. As seismic waves pass from one type of material into another, they are refracted (or bent slightly). As a result of these two observations, scientists have determined that all earthquakes have shadow zones.
What is the motion of secondary wave?
The S-wave (secondary or shear wave) follows more slowly, with a swaying, rolling motion that shakes the ground back and forth perpendicular to the direction of the wave.
What happens to the secondary waves S waves when it is approaching to areas with liquid composition?
Seismic waves move more slowly through a liquid than a solid. Molten areas within the Earth slow down P waves and stop S waves because their shearing motion cannot be transmitted through a liquid. Partially molten areas may slow down the P waves and attenuate or weaken S waves.
Why are there no S waves in the Shadow Zone?
The area beyond 105 degrees of distance forms a shadow zone. At larger distances, some P waves that travel through the liquid core would arrive, but still no S waves. The Earth has to have a molten, fluid core to explain the lack of S waves in the shadow zone, and the bending of P waves to form their shadow zone.
What happens in the Shadow Zone of an earthquake?
shadow zone The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves. The shadow zone results from S waves being stopped entirely by the liquid core and P waves being bent (refracted) by the liquid core.
Which is the best definition of a shadow zone?
Seismic Shadow Zones: P wave. The shadow zone is the area of the earth from angular distances of 104 to 140 degrees from a given earthquake that does not receive any direct P waves.
When was the Shadow Zone of the Earth discovered?
Through measuring how P and S waves travel through the earth and out the other side, a seismic wave shadow zone was discovered in about 1910. From the lack of S waves and a great slowing of the P wave velocity (by about 40%) it was deduced that the outer core is made of liquid. The shadow zone also defined the diameter of the core.