What you learned in school
Geology textbooks explained mountain formation through the "contracting Earth" theory. As the planet cooled from its molten state, it shrank like the skin of a drying apple, causing the crust to wrinkle and buckle upward into mountain ranges. Students learned this seemed logical - the Earth was like a cooling ball of iron with a rigid crust that had to crumple as the interior contracted. This "contractionist" theory dominated geological education for decades.
What we know now
Geology textbooks explained mountain formation through the "contracting Earth" theory. As the planet cooled from its molten origin, it shrank, causing the crust to wrinkle and buckle into mountains, like the skin of a drying apple. This seemed logical and was widely taught. Plate tectonic theory revealed that mountains form primarily through collision of tectonic plates, volcanic activity, and other dynamic processes. The Earth isn't shrinking - it's a dynamic system where new crust is constantly created and destroyed. Mountain building is an ongoing process driven by internal heat and energy.