Five oceans are in the world, which are the Arctic, Atlantic, Indian, Pacific and Southern.
Answer: D. It can melt to a depth of a few meters in summer, then refreeze in winter.
Explanation:
Permafrost is ground which remains frozen for two or more years. Permafrost consists of soil, rock and sand fused together by ice. Mostly found in areas in high altitude, the Arctic, Antarctica, it is common in periglacial environments where temperatures are below freezing
.
The topmost layer of permafrost can melt in summer and refreeze in winter. This thawing and refreezing produces a ground pattern called columnar joints similar to the one formed when molten lava cools.
During the second half of the 20th Century, a consensus emerged among North American archaeologists that the Clovis people had been the first to reach the Americas, about 11,500 years ago. This is the way America got populated.
<h3>What are major changes occurred in America's population?</h3>
In 2006, America's population reached 300,000,000 inhabitants. According to the estimates of the US Census Bureau, at the end of 2019 the American population will exceed 330 million people. As can be seen, it is a population in constant increase, both for its positive birth rate and for the high rates of immigration that arrive in the country every year. With these numbers, a percentage of annual population growth of 0.62% is determined.
This amount of population makes the United States the third most populated country in the world, only behind China and India (which have 1.4 billion and 1.35 billion inhabitants, respectively).
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The Mother Colony of the West Indies
The correct answer is B Subduction. Subduction is the process by which an oceanic plate gets dragged under another plate and is eventually destroyed in the mantle. Subduction occurs at convergent margins where two oceanic plates collide or an oceanic and Continental plate collide. Oceanic crust is made of mainly of silica and magnesium which is heavier or denser than continental crust which is composed mainly of silica and aluminium.
The subducting plate melts producing excess magma giving rise to volcanoes along these margins.
