In 60 years, from 1801 to 1862, the amount of cotton picked daily by an enslaved person increased 400 percent. The profits from cotton propelled the US into a position as one of the leading economies in the world, and made the South its most prosperous region.
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.
the answer is B. Stratovolcano
Stratovolcano is composed by one layer of hardened lava, volcanic Ash, and Tephra
These volcanoes are identified by their periodic explosive eruption, spitting highly viscous lava that could spread in a far distance
Answer:
C. The greater an element's density, the smaller the amount of it found in the crust
Explanation:
The layering of the Earth happened because of the different densities of the elements from which it was made. The denser elements started to sink deeper, the elements with medium density occupied the central part, and the elements with the smallest density remained at the surface. This resulted in the formation of the three basic layers of the Earth, core, mantle and crust. The core is composed of the densest elements, the mantle of the ones with medium density, and the crust from the ones with smallest density.
