Moss from the Sky

The air was nearly calm at Lake Minchumina that midwinter day when dirt, moss and other debris fell from the sky to dust the snow covering the lake ice. Nevertheless it was obvious to resident Florence Collins that the material raining down derived from the high Alaska Range 80 miles to the south or perhaps even the region of Cook Inlet beyond. Mrs. Collins could see plumes of snow blowing off the top of Mt. McKinley so she knew the wind was intense there. Further, reports on winds aloft that day, January 18, 1980, confirmed what she could see: 25 mph SE wind at 3000 feet, 45 mph S wind at 6000 feet, 61 mph S wind at 9000 feet, and 110 mph winds in the hills near Anchorage.

Recognizing the possible implications that observations of long-distance transport could have for studies of past climates and plant distributions, Mrs. Collins collected an envelope of the material that rained down and carefully recorded the circumstances. She delivered it to her friend Florence Weber, a geologist of the U.S. Geological Survey who has offices on the University of Alaska campus at Fairbanks. The envelope was soon in the hands of botanist James Anderson at the University's Institute of Arctic Biology, an expert in identifying pollen and paleo-botanical material.

In addition to the micaceous soil in the debris sample, Dr. Anderson was able to identify rather quickly at least sixteen different types of plant material. Included were leaves and leaf fragments of mosses and sedges, lichen fragments, portions of seed pods, spores, pollen from willow, sedge and black spruce and perhaps some charcoal. Some of these materials could be seen easily at ten times magnification, others required a hundred times.

Except for the black spruce pollen and perhaps the charcoal, the entire sample is compatible with a source in the high alpine tundra vegetation of the Alaska Range. The spruce pollen had to come from lower elevation, presumably from somewhere down on the southern flanks of the mountains or the lowland beyond--Dr. Anderson noted that the black spruce pollen is buoyant and likely to be carried long distances by wind.

Thanks to the perception of Florence Collins, the interest of Florence Weber and the detailed work of James Anderson, the moss fall onto Lake Minchumina gave a valuable lesson to all: unusual events or extreme variations from normal circumstances are not to be ignored when we try to understand how things got to be as they are.