While I'm on the subject of geology (when am I not??), I want to scream about just how COOL this rock is.
Just looks like an ordinary, uninteresting brown rock, right?
This, my friends, is an ophiolite. This is a rock that formed in the upper mantle. The minerals it’s made of (primarily olivine and pyroxene) are the most common minerals in the Earth, but don’t often make to the surface. The part of the lithosphere this formed in usually just sinks back down into the mantle in a subduction zone at the end of its life cycle.
But sometimes, in the right set of circumstances, pieces of the upper mantle can get pushed up onto the continent. The minerals in an ophiolite don’t like the low temperature/low pressure conditions at the surface. They quickly start to weather and form the non-descript brown color you see here instead of the green and black colors of the unaltered minerals.
But that’s not where this rock’s story ends.
At some point when this boi was chilling on the surface, a glacier came and picked it up. The glacier wore our rock smooth as it carried it over hundreds of miles before dropping it unceremoniously in a 5 meter thick layer of mixed up rocks and sediments that it laid down everywhere it went. It sat there in that layer of glacial till for thousands of years before coastal bluff erosion freed it and set it down on the beach. There it sat with other rocks from hundreds of miles away until a geologist who knows a thing or two about rocks (not me) picked it up and knew it wasn’t just another rock, but something unique that told a story about what happened not just to that beach, but to the earth hundreds of miles away and thousands of years ago.
Every rock tells a story in four dimensions.
Think about that next time you see one.
