Extent of the Markagunt gravity slide, now understood to be one of the largest terrestrial landslides known on Earth. The slide resulted from catastrophic collapse of the southwestern part of the Marysvale volcanic field about 21 to 22 million years ago. The ramp fault is where the slide mass moved up and over the former land surface. Insets show size of slide in relation to the state of Rhode Island and location with respect to the Marysvale volcanic field.