Explain why this statement is correct.
"Ice makes Antarcica both the lowest of the continental masses and the highest."
The statement "Ice makes Antarctica both the lowest of the continental masses and the highest" is correct because of a unique geological and environmental phenomenon present in Antarctica.
To understand this, we need to know that Antarctica is the southernmost continent, mostly covered by ice and snow. The statement is referring to the concept of "Ice isostasy."
Ice isostasy is a principle that explains the relationship between the thickness of ice and the elevation of land underneath it. When ice accumulates on land, it puts pressure on the Earth's crust, causing the land to sink or become depressed. This is known as "isostatic depression." Consequently, the thickness of the ice causes the land to be at a lower elevation compared to the surrounding ocean, making it the "lowest" among the continental masses.
Conversely, because the ice is so thick and accumulates over thousands of years, it weighs quite significantly. This immense weight causes the Earth's crust to sag further into the mantle, "floating" on a viscous layer. As a result, the underlying landmass of Antarctica is pushed down into the Earth, creating a sort of "mountain" underneath the ice sheet. This is known as "isostatic rebound." Therefore, Antarctica is also considered the "highest" when considering the surface level to the rock bed underneath.
Therefore, the combination of isostatic depression caused by the accumulation of ice on land and isostatic rebound resulting from the weight of ice causes Antarctica to be both the "lowest" and the "highest" of the continental masses.