My story began nearly 60 million years ago as hot magma erupting from a volcano. Upon exposure to to the cool temperatures of Earth's surface, I immediately solidified into what they call an "extrusive igneous rock".
Since I cooled so quickly from lava to a rock, there was no time for crystals or grains to form, and I was smooth- some may even say I was glassy.
Being a young volcanic rock was tough. It wasn't easy to withstand the frequent weathering; ice, wind, and rain scratched my surface daily. Eventually, I noticed fragments of myself chipping off. It reached a point where I couldn't even recognize myself anymore.
I realized then that I was undergoing erosion. I saw my fragments float away with the rain to a faraway stream. Over the course of the next 15 million years, I too joined my fragments in the stream. It was difficult to say goodbye to my life as an obsidian rock and accept that change was coming. I could no longer see the ocean either; it was a vast landscape of continental plates everywhere.
The next 10 million years went by rather slowly while I waited. Other sediments floated past, some staying and some going. I rested on the stream floor, patiently waiting as these sediments layered over me thickly. The pressure became so great that I started to undergo compaction with them. My fragments combined with the sediments began to weakly resemble rocks!
Dissolved minerals started crystallizing in the open pores of the rocks, which is what scientists call cementation. The minerals filled the available gaps, creating a more stable and cohesive form of my new self. I remember that I was a clastic sedimentary rock because my composition consisted of sand, gravel, and other assorted rock fragments.
I was also termed a conglomerate because of my large grains and visible pebbles. The abundance of clasts- another word for rock fragments- is why I was clastic! The entire process of deposition and lithification took a toll on me. I rested for another 10 million years on the stream floor, until I began to pick up on something strange..