The Forest and the Trees: Glacial Topography of the Central German Plain

Figure 1. Typical scene driving between Usedom and Goseck (See Fig. 2 for approximate location). The hills are glacial moraines as we saw at Usedom in the last post.

The wind blows pretty steady over the North German Plain and Central Uplands, so there are wind turbines everywhere, scattered among the hay fields (Fig. 1).

Figure 2. Map of central Germany, showing stops discussed in this and the next post. The red line is the (very) approximate path taken for this post.

The topography of the Central Germany Plain is very similar to Nebraska, Kansas, and the Dakotas, because they were all created by the advance and retreat of multiple glaciers during the Pleistocene Ice Age. As we saw in the last post, advancing ice sheets as thick as a mile push rock and soil in front of them, before melting back for a few millennia, leaving piles of soil and boulders behind. They are like gigantic bull dozers.

Figure 3. Gentle slope north of Berlin. This is a ground moraine, pulverized rock forming a thin layer of rich soil just waiting for the plows of modern farmers.
Figure 4. The hills in the background are either terminal moraines or eskers (another German word). See text for explanation.

As ice slides over the landscape, scraping off whatever gets in its way, the ice at its base can melt from the friction, creating streams that transport already ground-up rocks. The usual rules of sedimentology apply to these ice-encased streams. They can deposit their sediment load as eskers, which identify these sub-glacier streams, or as piles of scraped-off soil (terminal moraines). I don’t know which I’m looking at in Fig. 4, but this image gives a good impression of their impact on the landscape. Keep in mind that the ice was approximately ONE-MILE thick above the landscape shown in Fig. 4…

Figure 5. Entering the Saale River valley near Goseck.

As I alluded to in the previous post, geology isn’t a sequence of static processes; there is always more than one cause of what we see today, and none of them are stationary. Thus, the landscape produced by the continental glaciers that advanced over the Central German Plain during the Pleistocene were constantly in competition with alpine glaciers created in the valleys and peaks of the Alps. The huge ice sheets had the power to overcome any obstacle…but they couldn’t surmount the steep slopes of the Alps.

The glaciers that originated in the Alps waited until the last retreat of the great ice sheets that originated in Scandinavia, before they could make their play in the Holocene. Vast quantities of easily weathered feldspar were washed down their steep slopes into a panoply of rivers, which cut through the moraines left behind during the retreat of the continental ice sheets, creating broad river valleys like that of the Saale River (Fig. 5). Germany’s central plain and uplands were cut to ribbons by these growing streams, resulting in one of the most water-navigable regions in the world.

You always have to watch your back…

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  1. The Rest of the Story: The Harz Mountains | Timothy R. Keen - August 27, 2022

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