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Thursday, November 22, 2012

Concretions: An Interesting Stop on the Rock Cycle

Three friends and I recently took at kayak trip through the White Cliffs of the Missouri River in north-central Montana. We took time to do some short hikes to explore the fascinating geology of the area. During one excursion we hiked into the Eagle Creek drainage where concretions are especially abundant. Telling students about "concretions" is a great way to make the "compaction and cementation" (lithification) part of the rock cycle more interesting. Before you explain how they are formed, consider showing students photos of concretions* and then ask them to come up with a theory. To learn more about concretions CLICK HERE. Similar processes were also involved in the formation of the strange pedestal rocks, which we saw several miles downriver. To see 45 photos from our trip, CLICK HERE.

NOTE: If students have a good understanding of "plate tectonics" and "the rock cycle", they have a decent foundation in geology. For more about the rock cycle, check out this Rock Cycle PenCast.

*The links embedded in the above text will take you to several photos.

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