East Africa and the Basin and the Range Province of the United States are examples of a

Continental rifts

Explanation:

East Africa and the Basin and the Range Province of the United States are examples of present day continental rifts.

Rifting is caused when hot material from a mantle plume reaches the base of a continental plate and causes the overlying lithosphere to heat up. In addition to this the uwards movement of the plume against the base of the plate results in extensional forces, which can cause rifting. The East African Rift System is the most extensive continental rift system. Other examples are the range province of the United States, Baikal Rift in Russia.