Frankly, there is no single geologic event that I could definitly point out as being the most significant in my view. Surely, the Chicxulub impact at the end of the Cretaceous is a sensational event, just as much as as the first forms of life finding their way onto land or the Snowball Earth event as a drastic transition point in the history of our homeplanet. Still I am having troubles identifying an event in Earth History that truly catches my amazement.
What catches my amazement are the formations of different kinds of ore deposits, sediment being deposited, lithified, compressed to hard rock and then ripped apart by internal forces, fluids suddenly moving into the rock, dissolving it, alterating it and precipating new, fascinating components, potential valuable minerals, ores that are then eroded and transported by rivers only to be deposited again, perhaps lithified again.
But that is not an event to me. It is a process and a very long one that happened and happens over and over again in many parts of the world. So I think I am more fascinated by processes. However, we are looking for an event that caught my eye. I have one. A very personal one that happened not so long ago. Understanding Geology and processes behind it all. Grasping what it all means and how it all works.
How did I come to understand geology? By all those field trips, reading and - you may not be surprised - through the Geology of Mineral Deposits and their formation. It may seem strange but only when I began to be interested in how and why deposits form here and not there I also began to investigate the secondary conditions of tectonics, magma differentiation, fluid flow, paragenesises, sedimentology, petrology and palaeontology, etc. Within the last two or three semester the puzzle pieces began falling into the right places all by themselfs. Suddenly I would no longer be standing in a quarry but instead I was standing at the edge of a Mesozoic reef or the Palaeozoic outer shelf or maybe just on the shores of the North Sea - a million years ago. A schist would no longer be just a schist but it was begin telling me a story. I realised something very important: Everything is inter-connected! We are living in a huge, beautiful interconnected system. Nothing is truly isolated from the rest of the world.
I think two periods helped me greatly get to where I am today. My field trip to Brittany and my six months in Peru. In Brittany I understood not just the theory (that I could write down in an exam starting in the first semester) but I understood the implications and processes. There I could see the development in a few kilometers of beach from rifting, deep marine, shallow marine, etc. Then in Peru one day I stood on the beach below Larcomar and thought: "Damn! I am standing on a freaking Subduction zone with an Accretionary Wedge out there in the ocean!"
That gave me quite the shivers. But it was cool. Very cool. I am still at awe when standing in a valley and seeing the glaciers that formed it long ago or seeing a gem in a store and knowing that it can only come from a handful of places on the planet.
To conclude my geological event for this Accretionary Wedge: Understanding Geology and realising that everything is interconnected.
UPDATE: MJC and Ole also posted their contributions!
UPDATE 2: Callan, Geology Happens, Silver Fox, Tuff Cookie, Hypo-Theses, Andrew, Kim, Maria and Brian have now joined, too.