<p>Although parts of northern Minnesota have bedrock exposed at the surface (especially in the Boundary Waters area and along the short of Lake Superior), the more usual situation here is for the bedrock to be buried very deeply indeed - with, in places, more than a hundred meters of soil overlying it, according to <a href="https://conservancy.umn.edu/bitstream/handle/11299/60080/umn22629%5b1%5d.pdf?sequence=1&amp;isAllowed=y" rel="nofollow noreferrer">this map</a>.</p>

<p>This doesn't make sense to me; the whole area was buried under an ice sheet during the most recent glaciation, and the hundreds of meters of moving ice would have scraped everything down to bedrock (and scraped off large amounts of the bedrock itself) and prevented any new soil from forming until the ice sheet retreated.  Northern Minnesota has only been ice-sheet-free for a blink of an eye, geologically speaking - how did hundreds of meters of soil manage to form in such a short period of time?</p>

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2019-04-07T16:51:14.363Z
Glaciation also deposits a lot of material that was scraped away elsewhere, in the form of moraines, e.g. ground moraines and terminal moraines. Presumably much of the hundreds of feet of soil you refer to are just gravel and sand deposits, covered by only a few feet of more fertile top soil.
njuffa
<earth-history><soil><glaciation><bedrock><united-states>
Why is the bedrock buried so deeply in much of northern Minnesota?
Vikki
# Why is the bedrock buried so deeply in much of northern Minnesota?

(Asked by: username_0 on 2019-04-07)

Although parts of northern Minnesota have bedrock exposed at the surface (especially in the Boundary Waters area and along the short of Lake Superior), the more usual situation here is for the bedrock to be buried very deeply indeed - with, in places, more than a hundred meters of soil overlying it, according to [this map](https://conservancy.umn.edu/bitstream/handle/11299/60080/umn22629%5b1%5d.pdf?sequence=1&isAllowed=y).

This doesn't make sense to me; the whole area was buried under an ice sheet during the most recent glaciation, and the hundreds of meters of moving ice would have scraped everything down to bedrock (and scraped off large amounts of the bedrock itself) and prevented any new soil from forming until the ice sheet retreated. Northern Minnesota has only been ice-sheet-free for a blink of an eye, geologically speaking - how did hundreds of meters of soil manage to form in such a short period of time?

**Tags:** earth-history, soil, glaciation, bedrock, united-states

> **Comments:**
> **username_1**: Glaciation also deposits a lot of material that was scraped away elsewhere, in the form of moraines, e.g. ground moraines and terminal moraines. Presumably much of the hundreds of feet of soil you refer to are just gravel and sand deposits, covered by only a few feet of more fertile top soil.  

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## 0 answers

