Nature Notes

Volume XV No. 1 - September, 1949

The Frozen Lake
By Franklin C. Potter, Ranger-Naturalist

The biggest news of the year from Crater lake is that its surface froze solid in the winter of 1949. The lake that pamphlets said would never freeze because it was too deep has frozen; and, moreover, stayed frozen for almost three months.

An examination of the winter weather reports since 1926 reveals that the lake had never frozen during that time. However, in The Providence Manual of Information, compiled by the ranger-naturalist staff of 1934, H. H. Waesche reported that the lake was frozen over for two days in 1924. He adds that E. I. Applegate "suspects" that it was frozen at times during the winter of 1897-98 when the temperature at Fort Klamath reached -42° F. Although the lake often has skim ice sometimes over its whole surface, its resistance to freezing is due to the heat reservoir in the immense volume of water.

During the past winter the mean temperatures were lower than ever recorded. December had a mean temperature of 19, January 18, and February 22. The extremes were -9 December, -14 in January, and -8 in February. Considering that only eight out of 17 past winters had weather below zero, it was a cold winter on Mount Mazama.

A limnological survey of Crater Lake revealed that temperature stratification of the lake occurs at about 200 feet. Below that depth the water remains perpetually at 38 degrees. In the upper 100 feet the water temperature varies from 32 to 67, depending upon external factors; the highest temperature is near shallow shores. One reason that the lake fails to warm under the summer sun is a lack of suspended material which would absorb heat and warm the surface water. Because water becomes denser as it cools to 38 in colder weather there is some turnover in the upper layer, the warmer water rising from below. As the surface is cooled below 38 it becomes less dense and the water below imparts heat toward the surface, retarding ice formation. Crater Lake, with its great depth, stores a large amount of heat, even in water of 38 degrees.

This past winter a long period of abnormally low temperatures forced the upper water strata down to 32 degrees and the surface even lower. Heat absorption from the lake by the air was faster than convection of heat from the depths. Ice first appeared around the shoreline and gradually grew towards the center of the lake. After the surface was solid heavy snowfalls deposited four feet of snow on the two inches to one foot of ice. Now that it is known that the lake can freeze under certain conditions, another delicate environmental balance is added to those which determine the character of the mountain and the lake.

The Little Beggars Are Scarce
By Ralph R. Huestis, Ranger-Naturalist

golden-mantled ground squirrel

The golden-mantled ground squirrel, which certainly affords park guests as great an amount of entertainment and opportunity for behavior study as any member of our wildlife group, was only moderately common during the 1949 season. Good indicators of the size of the squirrel population are the maximum number of squirrels that can be seen at one time at the head of the Lake Trail and the number of squirrels resident in the upper part of the Rim Camp area. To see twelve squirrels at a time at the head of the Lake Trail, and all of them big ones, means a big park population. Sample observations made during 1949 gave the writer an eight squirrel maximum and a mode of four. Some of the squirrels were yearlings and one was even a young of the year. No such callow operative could have maintained a pitch there during the roaring 30's. He wouldn't have lasted an hour. One squirrel only has been around the upper Rim Camp area.

Young of the year came out of maternal burrows in the rim area during the first week of August, 1949, in numbers much under modal, and gave no support to the theory that a rather sparse population of adults is necessarily favorable to population replenishment. In 1947 squirrels were so plentiful on highway 230 that they constituted a driving hazard. This year the area is so largely deserted that it must be concluded that squirrel scarcity is a more than local phenomenon. Be that as it may, the individuals that are with us are acting as though they are convinced that lean squirrel years need not necessarily produce lean squirrels.

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