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How Much Sand is There? More Sand than Meets the Eye!

How much sand is in the sand dunes? The simple answer is "a lot," approximately 4.8 billion cubic meters, but that is really just the tip of the iceberg. The dunefield is impressive with its tall dunes and scenic backdrop, but it is the smallest of three sand deposits in the Great Sand Dunes system, measuring just 30 mi2 (78 km2). In the valley surrounding the dunefield is the sand sheet, covering 180 mi2 (466 km2). Close examination shows how the sand sheet got its name; it is almost 100 percent sand and, despite some small hills and depressions, is primarily flat. Farther west in the valley, near the San Luis Lakes, lies the third sand deposit, the sabkha. It extends over 120 mi2 (311 km2) and is characterized by sand grains cemented together by minerals.

The active dunefield

The sand sheet

The sabkha (aerial view)

Why are dunes only found on 30 of 330 mi2 (855 km2) of sand deposits? Dune formation requires several conditions. First, there must be sand! Wind strong enough to move the sand (>13 mph or 21 kmph) must also be present. Both sand and wind are plentiful, so the key factor is that sand must be loose and moveable. The sand in the sabkha is hardened by minerals, so the wind cannot shape it into dunes. On the sand sheet, vegetation anchors sand, preventing dune formation. If you look across the sand sheet, however, you can see tan-colored areas where the vegetation has lost its foothold and dunes are forming. Sand in the dunefield is completely exposed to the wind and, as a result, dune formation is very active.

The sand sheet and sabkha are subtle features, but you can discover them as areas undeveloped for human use. Coming from the west on Lane Six, the farmlands end where the sabkha starts. Travelers using Highway 150 will notice a lack of houses west of the highway until they near Highway 160; that is the sand sheet. Since the land in both areas is sand, it is not suitable for farming or home sites.

These varied sand deposits played an important part in the legislation passed in late 2000. The condition of the two larger deposits greatly influences whether new sand comes into the dunefield; the expansion is intended to help protect the natural processes of sand replacement occurring in those areas. by Andrew Valdez