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Magmatic FeatureS:

stoping

Look at the image below of a rock from Yosemite!

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Can you see some grey, circular "blobs" in the granitoid? What are those? How did they get there?

The grey "blobs" in the image are called stoped blocks and they form due to a process called stoping!

Stoping [ stoh-ping ] is the process by which magma causes the breakage and separation of intruded rock (also called the host rock) due to its upward motion. If that is hard for you to visualize, don't worry! We will explain stoping more in an upcoming video.

But first, in order to better understand the process of stoping, listen to this audio clip of something that you may hear in your everyday life. Can you guess what the sound is?

REVEAL THE ANSWER

How does this example apply to stoping? Watch the video below to get a better understanding of this magmatic feature.

Now that we understand stoping, let's apply it to relative dating!

According to the Principle of Inclusions, the stoped blocks from the host rock must be older than the granitoid because in order for the magma to break the rocks apart, the rocks had to exist first.

Let's see some more photos of stoping from Yosemite!

Stoped blocks are a bit difficult to find in Yosemite because the majority of our host rock has disappeared over time due to uplift and erosion. So in order to find some stoped blocks, we will need to explore a bit!

Let's go on a hike! (virtually of course)

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It seems that we have to travel very far to find some stoped blocks...

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but the views make it worth it!

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Now that we've hiked for a while, it's time to look at some stoped blocks! Roll your cursor over this image to find the stoped block (from the host rock) in this image!