Why do External Tanks on space shuttles burn up when entering the atmosphere?

External tanks on space shuttles burn up upon re-entry due to their composition and the extreme heat generated by atmospheric friction. Made primarily of lightweight materials like aluminum, these tanks are not designed to withstand the intense temperatures and pressures experienced during re-entry. As they descend, the friction with the atmosphere generates temperatures that can exceed 3,000 degrees Fahrenheit, leading to the combustion of the tank's material. Ultimately, this results in the tanks disintegrating and burning up before reaching the Earth's surface.