Sarah here –
I recently went on a trip with my husband to Maine, USA and New Brunswick, Canada to see some of the best geology these places had to offer! I’ll be showing you a lot of the gorgeous geology (and some cool biology!) through a series of posts. This first post will be all about my trip to Acadia National Park. My husband and I hiked quite a few trails (about 20 miles of trails total!) in the four days we were there and we learned quite a lot about the geology of the park from our adventures.
A lot of the rock you’ll see in the popular parts of Acadia- especially the trails in the main part of the park-will be granite. Granite is an igneous rock that formed intrusively, meaning, it formed under the surface of Earth. You can generally tell whether igneous rocks formed intrusively or extrusively (on Earth’s surface), because the sizes of the grains will be different. The magma that makes up granite cools very slowly under the surface of Earth-the slower it cools, the larger the crystals are! But, I digress. Many of the mountains in the Acadian region are made of granite. This granite was formed when two continents- Laurentia (North America) and Avalonia (eastern North America and western Great Britain) slammed together hundreds of millions of years together. When they collided, it forced a huge amount of magma to pool, creating the famous granite we see today (you can read a lot more about the creation of Acadian rocks at this site)! Here’s a photo of me climbing some of this granite on the Beehive Trail! The mountain is very steep and the trails are very narrow, so it is most safely climbed using metal ladders!
Granite is a very hard, stable rock. What that means is that it doesn’t weather away easily, like other rocks (think of how marble gravestones look like after a few decades-marble is much more easily worn down!) But after millions of years, even the toughest of rocks can start to be broken down! Take a look at these rocks here-you can see the cracks from being weathered (likely by rain!)-these cracks allow rain to penetrate into the rock and break it down even faster! To put it into perspective, think of a windshield-if you put a single crack into it, you’ve weakened the glass and further pressure can result in faster spreading of the break. Rocks respond similarly after the first cracks are formed!
I want to show you some of the cool pictures from the other side of Acadia now. This is a lesser known, but just as beautiful part of the park as the most well known part of Acadia. This area is called Schoodic Point. This is also dominated by the same gorgeous granite-but it’s got something else going on that’s really spectacular. If you take a look, you’ll see the gorgeous light colored granite…but also, intrusions of a dark colored igneous rock (called a diabase); this diabase has tiny crystals-meaning, it cooled quickly! We can tell that the dark colored rock intruded into the granite because of the Principle of Cross Cutting Relationships; this geologic principle means that if a rock “cuts across” another rock, the rock that is cutting across is younger (read more about geologic principles here).
So, with that in mind, these diabase intrusions are the remnants of later episodes of volcanic activity. There are multiple episodes of volcanic activity represented here-many of the intrusions are cut by even more intrusions! What a beautiful place. So even though this is a post about geology, I wanted to show you a little bit of the life here at Schoodic Point-the wave activity at this area is VERY high (one easy way to see that is that there’s very little sand at this coast-the wave energy is too high, so the sand gets washed away). The water crashes up onto the granite and some water will stay up there, giving a perfect spot for lots of little critters to form a home! Take a look at this small pool of water-how many critters can you see?
Stay tuned for more posts on the rest of my trip!