What might explain the patterns of population density in northern Africa?

Melting glaciers is a serious threat to the environment what is the possible consequence of melting glaciers on polar bears?

Which set of characteristics best describes sedimentary rock? a) largest type of rock, made of organic matter, hardest type of rock b) often contains layers, forms near sources of water, contains fossils c) least abundant type of rock, made of other rocks, made mostly of minerals d) most abundant type in earth's crust, made of magma/lava, contains no fossils

What is the identity of the planets?