The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken up into tectonic plates. The Earth's lithosphere is composed of seven or eight major plates (depending on how they are defined) and many minor plates. Where the plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The relative movement of the plates typically ranges from zero to 100 mm annually.[2]
Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle; the material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total surface of the lithosphere remains the same. This prediction of plate tectonics is also referred to as the conveyor belt principle. Earlier theories, since disproven, proposed gradual shrinking (contraction) or gradual expansion of the globe.[3]
Tectonic plates are able to move because the Earth's lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the spreading ridge (due to variations in topography and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones. Another explanation lies in the different forces generated by tidal forces of the Sun and Moon. The relative importance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.
Answer:
Because, a natural hazard is a threat of a naturally occurring event will have a negative effect on humans.
Explanation:
They have less-runny lava, meaning that it doesn't travel as far before cooling, meaning that the layers build up more steeply, but don't go out as far. You also get layers of ash on the composite volcano to help build it up too
Answer:
Apartheid was a system of forced migrations
Explanation:
Also, there was a lot of slave trading. Also, it was pretty common for slave owners to breed with their slaves
The correct answer is - the Americas.
The Americas from what is known and discovered till now are by far the latest continents that were settled by the people. Even though it is still not clear when exactly did this happened it is in the range between 19,000 and 12,000 years ago as the biggest given and lowest given number by scientists. It is understandable though that people found it hard to migrate in this part of the world since it was cut of by an ocean and the only way that they could migrate was through the Bering Land Bridge which in fact was an icy bridge between the continents and extremely inhospitable place. There is also the large carnivores in North America as a factor that delayed the migration, and of course the ongoing ice age which covered huge portions of North America with glaciers, ice and snow.
