Why I Like Geology

26 Mar

If I could do it all over again, I’d be a geologist!

Earth science is fascinating to me. I like thinking about the Earth that used to be, the Earth that might be in the future.  I like looking closely at the rocks and imagining what kind of world created them, and thinking about how they’re currently dying and being destroyed to start the cycle over.  My daughter wanted to study plate tectonics for her science fair project, so I suggested we drive around and look for evidence of tectonic activity just outside town.  In northern Colorado, there are rich and interesting places to study geology and I thought it would be a shame for her to do an earth science project at a desk!  So we drove around and looked at rocks.

We found marine fossils embedded in the limestone near home.

Sea creatures

Sea creatures

We dug into the shale at a roadcut.

Uplifted shale

Uplifted shale and Dakota Sandstone

We ran our fingers over the conglomerate at a rock climbing area.  I marveled at the Morrison Formation under our feet, which has yielded a very rich trove of dinosaur fossils over the years.  Who knows what could be right under us!

Conglomerate. Once, there was a mountain. Pieces of it washed away and got cemented into a new rock, then that rock got uplifted and became.. a new mountain

Conglomerate. Once, there was a mountain. Pieces of it washed away and got cemented into a new rock, then that rock got uplifted and became.. a new mountain

We felt the gritty sandstone at base of the red cliffs of the Fountain Formation, like bookends on either side of a mountain.



We visited Horsetooth Mountain Park and examined the ancient schist and pegmatite.


It’s all metamorphic and schist.

Pegmatite granite. Igneous

Pegmatite granite. Igneous rock


We downloaded a free geologic map from the USGS for the project.  What a wonderful resource!  My kid organized her rock information and made a presentation board, and of course I keep thinking and thinking and thinking about rocks.  It made me understand the reasons I like geology as much as I do.  As a “math person”, it appeals to me because it has logic-puzzle features.  I like looking at the evidence around me and reasoning out the history of the area.  As with all logic puzzles, there are a few simple rules and likely only one correct solution.

– Sedimentary rocks are created in more-or-less flat layers.  Newer layers are always created over the top of older layers.
– Igneous rocks can intrude into other rocks.  If an igneous formation cuts through another rock formation, it’s newer than the surrounding rock.
– Faults can cut through other rocks.  A fault is newer than the rock it cuts through. Rock that overlays and covers a fault is newer than the fault itself.  Uplift happens after the sedimentary rock has been deposited.

I know less about the formation of metamorphic rocks and so my rules for them are incomplete.  But using what I know, I can look at the map and at rocks around me and build a geologic history of the area.  The rocks had to have been created in a certain order, and so a story starts to weave itself.  First there was rock, and then metamorphism, and then igneous intrusions, and then came the sandstone, then some faulting, then the shale and the dinosaurs, then more sandstone and then more dinosaurs, and then there must have been a time of erosion, and then more faulting and so on and so on.  I like to look at the map to see if I came to the same conclusion as the geologists who made it.

As much as I want to help my kid learn about the scientific method, all I keep thinking about is what a cool puzzle it is to piece together the history of northern Colorado!  Is that science, or more mathematics?


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Posted by on March 26, 2013 in Outside the Classroom


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