The relief forms of glacial origin

The characteristic big relief forms of South Estonia are accumulative uplands of uneven surface, and depressions and vales separating them. Hillocky relief was formed during the final period of the last Ice Age, when the edge of ice remained in these areas for a longer period, and a lot of debris located inside and on the surface of the ice was released when the ice melted. Bigger relief forms separating uplands are depressions and vales. Depressions are closed relief forms, the bottoms of which are usually covered with peat. Vales are elongated open wide-bottomed relief forms of indistinct shape. Along the bottoms of such vales flowed giant rivers at the end of the Ice Age, which by now have diminished to small streams.

The layer of Quaternary cover extends to a depth of 100 m in some places, and its composition varies greatly. Drilling has revealed sediments deposited during several glaciations, the oldest of which usually fill buried primeval valleys. The modern relief, consisting of hillocks of different size and shape, ridges, and depressions and short valleys between them, was formed by the sediments of the last glaciation.

The relief of accumulative uplands is a combination of relief forms of extremely complex nature. We can see numerous small hummocks consisting exclusively of till. The interior of slightly bigger hillocks usually consists of gravel and sand, covered with a thin layer of till. The composition of the biggest hillocks and ridges is usually the most complex. Quite often their interior consists of gravel and sand, but is covered with varved clays, accumulated in local ice-dammed lakes, such as Kuutsemägi or Juusamägi on the Otepää Upland and Vorstimägi on the Haanja Upland. There are also oblong end moraines (Kambja Köstrimäed on the Otepää Upland), and even areas of dense eskers, such as kame-esker fields on the southern and southeastern parts of the Karula Upland.

The shapes of positive relief forms vary greatly. In the central part of the Karula Upland there are hummocks of rounded shapes with slopes steepening towards the foot, the best-known and most beautiful of these are located at Kaika. The central part of the Haanja Upland is characterised by numerous complex relief forms, where smaller hillocks have accumulated on the surface of oblong ridges, which are cut by deep gullies. Small rounded depressions between hillocks were formed only after the withdrawal of the glacier when blocks of dead ice, buried deep under sediments, melted much later, causing the sinking of the surface. Such basins are called glaciokarst depressions, and small lakes or mires can usually be found in their basins.

The areas where deep primeval valleys traverse hillocky relief are the most variegated and beautiful parts of uplands. The valleys are steeply sloped, and chains of lakes lie at their basins. The most prominent valleys of the Otepää Upland are the Vidrike, Kooraste and Urvaste valleys; the Rõuge primeval valley is the best-known valley of the Haanja Upland. The latter has a number of short but deep side valleys, such as Hinni Canyon. With its almost vertical walls and sandstone outcrops, and ancient trees that have fallen into the canyon, it looks like a real wilderness. Deep valleys can also be found on the northern slope of the Haanja Upland. The best-known among them is Kütiorg. On the southwestern slope of the upland there is an interesting transition zone between the Devonian sandstones and limestones. Over a short distance of only a few kilometres we can find the outcrops of both sandstone and limestone. The latter can best be seen at the Kalkahju outcrop at the village of Karisöödi.

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