Ocean. Additional sedimentation occurred until a subduction zone formed off the coast. The subduction uplifted the region out of the sea and created a line of volcanoes. Later the crust started to pull apart, creating the current Basin and Range landform. Valleys filled with sediment and, during the wet times of glacial periods, with lakes, such as Lake Manly. Death Valley is the fifth-largest American national park and the largest in the contiguous United States. It is also larger than the states of Rhode Island and Delaware combined, and nearly as large as Puerto Rico. In 2013, Death Valley National Park was designated as a dark sky park by the International Dark-Sky Association. Geographic setting There are two major valleys in the park, Death Valley and Panamint Valley. Both of these valleys were formed within the last few million years and both are bounded by north–south-trending mountain ranges. These and adjacent valleys follow the general trend of Basin and Range topography with one modification: there are parallel strike-slip faults that perpendicularly bound the central extent of Death Valley. The result of this shearing action is additional extension in the central part of Death Valley which causes a slight widening and more subsidence there. Uplift of surrounding mountain ranges and subsidence of the valley floor are both occurring. The uplift on the Black Mountains is so fast that the alluvial fans (fan-shaped deposits at the mouth of canyons) there are small and steep compared to the huge alluvial fans coming off the Panamint Range. Fast uplift of a mountain range in an arid environment often does not allow its canyons enough time to cut a classic V-shape all the way down to the stream bed. Instead, a V-shape ends at a slot canyon halfway down, forming a 'wine glass canyon.' Sediment is deposited on a small and steep alluvial fan. At below sea level at its lowest point, Badwater Basin on Death Valley's floor is the second-lowest depression in the Western Hemisphere (behind Laguna del Carbón in Argentina), while Mount Whitney, only to the west, rises to and is the tallest mountain in the contiguous United States. This topographic relief is the greatest elevation gradient in the contiguous United States and is the terminus point of the Great Basin's southwestern drainage. Although the extreme lack of water in the Great Basin makes this distinction of little current practical use, it does