June 2018
Salish Sea, Pacific Northwest
With the summer solstice imminent we’re getting some extreme low tides these days. This day I went down to check out a bouldery beach nearby.
Where did this bounty of variously colored and patterned boulders come from?
Over the past 2 million years, during a series of Ice Ages, glacial sheets rolled over vast areas of territory as they spread south, picking up rocks along the way. When the glaciers melted, the rocks fell out, sometimes many hundreds of miles from their source.
The most recent glaciation had its maximum extent about 12,000 years ago. It reached about 150 miles south of this beach, so when it began to retreat, a whole lot of rocky material, from sand grains to giant erratics, were deposited in the Salish Sea area. Differential wave action along the shore sorted sediment in such a way as to leave each beach with its own set of loose rocks. This particular beach is mostly composed of boulders baseball to basketball size with a few bigger ones (unlike the last beach rock Bucket I did at a different beach which has mostly ping pong ball size cobbles).
The Daily Bucket is a nature refuge.
We amicably discuss animals, weather, climate, soil, plants, waters and note life’s patterns.
We invite you to note what you are seeing around you in your own part of the world, and to share your observations in the comments below.
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Here are a few of the rocks that struck my fancy yesterday.
Headlands at the ends of beaches are resistant bedrock, which is why they stick out. At any given beach, the bracketing headlands are not necessarily the same kind of bedrock. The near end of this beach is “Jurassic-Cretaceous, slightly metamorphosed and sheared sandstone and mudstone” according to Western Washington University geologist Dave Tucker.
Got rocks where you live?
What’s up in your natural neighborhood today?
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