Because as they travel through the earth, the density of the material through which they are travelling will vary. This causes the speed of the wave to change which in turn results in a process known as refraction where the waves direction of propagation changes. As the density of the material in the earth continually increases with depth due to the increasing overburden pressure, the speed of the seismic waves will continuousy change with depth leading to continuous small changes in propogation direction which leads to the formation of a curved propagation path.
Geophysicists make use of this phenomenon to estimate the density and structure of the interior of the earth.
For more information, please see the related links.
Waves are refracted gradually because they change speed as the density changes gradually.
Changes in the density of the material through which the waves are travelling.
We know based on the timing and paths taken by seismic waves that such waves travel through different parts of the Earth at different speeds.
It causes the currents to move in curved paths instead of going in a straight line, which is known a the Coriolis effect.
The paths of seismic waves
headward erosion
The speed of the waves that travel through the interior can tell the density of each layer of the Earth. Some waves can make it through certain layers, but not others.
Very often tornadoes, will travel in a straight line, but many do not, following meandering or curved paths instead.
We know based on the timing and paths taken by seismic waves that such waves travel through different parts of the Earth at different speeds.
Two main reasonsthe surface of the earth is not smooth so currents have to travel in curved paths to get around obstaclesCoriolis forces - because of the huge distances involved the differences of forces due to the changes in the circumference of the earth at different latitudes causes currents to curve even if they are trying to travel in a straight line. Note: it takes huge distances - on the order of miles - to see any effect from Coriolis forces (- despite the urban folklore out there about drains swirling different directions in the Northern and Southern hemispheres. Hint - they don't) Unless your sink or toilet is miles across, you won't be seeing Coriolis forces determining the direction of swirl as they drain.
Earth's rotation causes the water to move in a curve; this is a manifestation of The Coriolis force.
It causes the currents to move in curved paths instead of going in a straight line, which is known a the Coriolis effect.
Because as they travel through the earth, the density of the material through which they are travelling will vary. This causes the speed of the wave to change which in turn results in a process known as refraction where the waves direction of propagation changes. As the density of the material in the earth continually increases with depth due to the increasing overburden pressure, the speed of the seismic waves will continuousy change with depth leading to continuous small changes in propogation direction which leads to the formation of a curved propagation path. Geophysicists make use of this phenomenon to estimate the density and structure of the interior of the earth. For more information, please see the related links.
gravity
Because of the Coriolis Effect
Bezier
Geologists record the seisemic waves and study how they travel through Earth. different types of waves behave differently. The speed of the waves and the paths they take reveal the structure of the planet. That's all I know................................
It is due to the earth's rotation. (source: January 2005 earth science regents exam)
Technical answer: The reason light cannot escape, is because a strong gravity will bend space time. Light follows curved space time. Inside the extremely curved space time of a black hole, it is so curved that all paths bend back on themselves to the singularity. Light, which follows these paths through space time, bends back on itself and ends up at the singularity.