Our transcription: So apart from some xenoliths, walking across a complete ophiolite section is the only other way geologists have of directly viewing rock from Earth's mantle.
I have come about a quarter mile from our last stop, which was in the lower part of the ophiolite.
There the rocks looked like this: dark, because they are rich in the minerals olivine and pyroxene, which are typical of the Earth's mantle.
The rocks I am standing on now are lighter colored, primarily because they are rich in the mineral feldspar, the white mineral you can see in this rock.
In coming the quarter mile, I have walked from the Earth's mantle into the Earth's crust.
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