The U.S. dust storm of February 1977
The strong winds of the first winter storm to reach the drouth-stricken High Plains in February 1977 caused the largest dust storm yet observed by geostationary orbit environmental satellites (GOES). Two dust plumes, one in eastern Colorado-western Kansas, another near the Texas-New Mexico border, were first observed on GOES-1 images taken at 1700 GMT February 23, and the east-south-eastward progression of the dust pall was observed on later images. By 2030 GMT February 24, dust totally obscured about 400,000 km2 of ground surface in the south-central United States, as seen on satellite pictures. By 1600 GMT February 26, a discrete dust pall was still visible over the mid-Atlantic Ocean. The enormity of this single dust storm and the historical recurrence of such events suggest that atmospheric transport of dust eastward from the Great Plains to the Atlantic Ocean is of sedimentologic significance.
One point source of the dust, the Clovis-Portales area, New Mexico, has a long history of episodic aridity and associated eolian activity that extends from Tertiary time to the Dust Bowl events of the 1930s and similar occurrences during the 1950s. The authors have investigated wind erosion and deposition due to the February 1977 storm by aerial and ground reconnaissance of this area, which is in the windiest part of the southern High Plains. During the 1977 storm, plowed fields were locally eroded to depths of greater than 1 m, and myriads of small yardangs were formed. Fine sand winnowed from certain vulnerable soils was deposited in lobate sheets from several centimetres to more than a metre deep that extended several kilometres downwind from the plowed fields and blowouts.
Several key factors contributed to the severe effects of the storm. A persistent Pacific high-pressure ridge, which had diverted earlier storms northward, contributed to a prolonged drouth in the Great Plains. Breakdown of this high permitted passage of the first winter storm into the region, accompanied by very strong winds. Soils of the Portales Valley, composed mainly of eolian sand, silt, and clay, were unusually dry and vulnerable to the wind, which accelerated suddenly on the morning of February 23. The erosive power of the wind in that area may have been further enhanced as it blew upward over the cap-rock escarpment of the Llano Estacado. Other factors that probably contributed to the severity of wind damage from this storm included certain land-use practices that had resulted from a coincidence of economic conditions and governmental policies.