Sastrugi Sastrugi Sastrugi, or zastrugi, are sharp irregular grooves or ridges formed on a snow surface by wind erosion, saltation of snow particles, and deposition, and found in polar and open sites such as frozen lakes in cold temperate regions. The ridges are usually perpendicular to the prevailing winds; they are steep on the windward side and sloping to the leeward side. Smaller irregularities of this type are known as ripples (small, ~10 mm high) or wind ridges. Larger features are especially troublesome to skiers and snowboarders. Traveling on the irregular surface of sastrugi can be very tiring, and can risk
Origin of the Oak Ridges Moraine a 20 m layer of shallow surface Oak Ridges Moraine sediments, underlain by the "Newmarket Till". The other wedges, which peak at up to 335 m, have thicker and more varied surficial deposits, and the "Newmarket Till" lies deeper below the surface. Moreover, the sedimentary deposits are underlain by "Halton Till" on these wedges, which is not present in the Rice Lake wedge. Thus, from top to bottom, the stratigraphy of the moraine is: The most accepted theory of the development of the Oak Ridges Moraine is that proposed by Barnett et al. (1998). "Moraine development is highlighted in four