Geology | Santiago Rock Formation

After driving for hours, a beautiful rock formation in Santiago, Ilocos Sur finally showed itself.

Being a geology undergraduate, my coursemates and I usually go out for fieldworks (and this, perhaps, is the best thing in my course). Just last semester, we went to Ilocos Sur. We were assigned to look at different rock formation or outcrops.

From reviewing literature and listening to class discussions, the area of Ilocos Sur is generally sedimentary in composition. As such, we were tasked to analyze various outcrops and study the order, position, and relation of layers to each other.

I really want to share with you the wonders of geology, but I don't want to bombard you all with geology jargon. So I'll try my best to keep things short and sweet!

From afar, the tilted layers of the Santiago rock formation are very evident. It might not be noticeable, but it is actually quite a very large outcrop reaching at most 20 feet high. It is also generally heavily weathered with little vegetation.

Upon closer look, the layers are actually made of two alternating rock types: sandstones and mudstones. I say this because rock samples of those two layers revealed two rocks with different grain sizes. The finer or smaller grained one was the mudstone while the one with coarser or larger grains was the sandstone.

To confirm that the rock types were indeed sedimentary, they bubbled or effervesced when I put diluted acid on them!

The Santiago outcrop was just one of the many more rock formations we saw in our fieldwork. I'll definitely share the others with you in my future posts (including the other places we went to)!

If you have any questions or you're curious about geology, feel free to comment! And if you liked this post, please comment, reply, or even follow!