The accretion process probably lasted for several thousand years before the moon was fully formed. Models suggest that impacts accompanying accretion caused heating of Ariel's outer layer, reaching a maximum temperature of around 195 K at a depth of about 31 km. After the end of formation, the subsurface layer cooled, while the interior of Ariel heated due to decay of radioactive elements present in its rocks. The cooling near-surface layer contracted, while the interior expanded. This caused strong extensional stresses in the moon's crust reaching estimates of 30 MPa, which may have led to cracking. Some present-day scarps and canyons may be a result of this process, which lasted for about 200 million years.