Which of the following occurred about 21,000 years ago?
(a)-india breaks off from antarctica and begins moving north toward asia.
(b)-the formation of the ice age glaciers.
(c)-the appalachian mountains finish forming.
(d-)the north atlantic ocean begins to form.

(b) The formation of the ice age glaciers occurred about 21,000 years ago.

Explanation:

The last glacial period occurred in the period between 115,000 - 11,700 years in the past with the recent glacial period called Quaternary glaciation. Though some call this period the last ice age, it is a wrong definition because ice age is defined by year-long ice which still persists in the Antarctica and Greenland. The last glaciation that occurred 21,000 years in the past, is the last glaciation on Rocky Mountain.

It occurred in the period 31,000 - 10,000 years and between 23,500 - 21,000, it was at its highest. The glaciation was not made of the giant ice sheet but was made of mountain glaciers known as Cordilleran Ice Sheets. These sheets produced Lake Missoula which late caused Missoula flooding.

brave new world, aldous huxley (1932)

heat from the core of the earth causes convection currents to occur in the mantle. these currents slowly move the crust around.