Antelope Island Field Trip, and A Very Gneiss Day

We read that Antelope Island has deposits of gneiss from the Farmington Canyon Complex, which contains some of the oldest rocks in the United States. The gneiss in this area is 1.7 billion years old---as old as the rocks at the bottom of the Grand Canyon! We've never been to Antelope Island, and it was a lovely day, so we called some friends and headed up there for a picnic and to find some gneiss!

You drive across a 7-mile-long causeway, over the Great Salt Lake, to get to the island. There was lots of stark, interesting scenery, like this smooth, dead tree stump in the middle of a salt marsh.

The island is really beautiful. It smells like the ocean!

One fascinating thing you can see there are the herds of American Bison, about 600 of them, that we learned were introduced to the island in 1893. (Side note: I learned a long time ago that "bison" was the more accurate name for what we usually call "buffalo," but in fact Wikipedia tells me that both are equally correct. This is good, as my friend Andrea kept singing "Man on a Buffalo" and I'm sure she'll be thrilled to know that she can sing on, unhindered by the less melodious term "bison.")

There are pronghorn, too (the eponymous "antelope" of the Island)---see them down on the sand there?

We loved the bison/(buffalo)(s). (Argh, now that I've got their names straightened out, I'm unsure if buffalo or buffaloes is the plural! The words bison and buffalo are both unchanged by the plural---I think. Okay, looked it up, and it looks like buffalo or buffaloes is acceptable, but bison is plural and singular. Thank you; I hope this parenthetical statement has been educational.) They were so huge! And they came really close to us, so we could get good looks at them from our car. Beautiful animals!

My great fear during this little excursion was that I would not be able to recognize the gneiss when I saw it. And everyone was counting on me! I knew what gneiss looked like in our rock field guides, but I didn't know if this would be NICE gneiss like in the books. Or some sort of inferior gneiss that didn't look very gneiss-y.

The gneiss was supposed to comprise the Southern 2/3rds of the island, and to my great relief, as we drove along, we saw this ^^^

Gorgeous, beautiful, textbook gneiss! You can't miss it. I was so glad.

We got out and climbed around. Gneiss is such a cool-looking rock!

Pretty mineral crystals incorporated into this rock (Cowan found these)

While we looked at the gneiss, storm clouds started to gather, making the setting really beautiful and dramatic.

What an amazing setting! I call this series "Gneiss Weather Ahead."  Hahahaha!

We got back into our cars just as the rain hit, and then we were treated to some spectacular clouds moving across the lake. So pretty!

We were so reluctant to leave, because it was a most perfect and interesting day. As we drove away and the rain subsided, we watched (and listened to!) this buffalo drinking water from a puddle on the road. *SLURP SLURP SLURP!* He made such funny noises.

The sunset behind the dark clouds was so lovely.

And that was all---except for us passing this Important Landmark on the way home :)

Chocolate Rock Cycle

Now, to put all this information together in the Rock Cycle! There are lots of ideas online about how to simulate the rock cycle. You can use crayon shavings, but we used three types of baking chips---chocolate chips, peanut butter chips, and white chocolate chips.

You can start the cycle at any point. We started by "weathering" various rocks and minerals (the baking chips) into smaller sediment. We used graters, paring knives, and a microplane grater to do the weathering. You want some very small pieces, and some larger pieces, of each type of baking chip.

Sprinkle a little bit of each type of sediment onto a piece of foil. Wrap it up tight and then add some pressure. You can squeeze it tightly between your hands (this adds a bit of heat) and then stand on it. Put a book on top to distribute your weight evenly.

Unwrap the foil to see your sedimentary rock! Each person's "rock" will be a bit different, based on the rocks and minerals that it is composed of. Be careful when handling these rocks because they are quite fragile.

Now add more heat and pressure to make a metamorphic rock. We re-wrapped our rocks tightly in the foil and then floated them on some hot water for 10 seconds or so. (You don't want to melt the chocolate completely.) Press the foil between your hands again to add more pressure. Then put the rock (in its foil packet) into the refrigerator to harden for several eons (10 minutes or so). :)  Unwrap it to see your metamorphic rock! You can observe, at this point, that some of the "minerals" making up the rock are more melted and disfigured than others. This is true to nature, as different minerals have different melting points and will also re-crystallize at different temperatures.

Igneous rocks are next. Take your metamorphic rock, re-wrap it in foil, and float it for a longer time on some hot (even boiling) water.

Sometimes a little bit of water leaked into our foil "boats." It's okay.

Unwrap, take a toothpick, and stir the melted rock and minerals around. This is "magma," and you are creating convection currents in it.

Refrigerate the rock again until it's hard. Now you have an igneous rock! The minerals are still present, but you can no longer see them as individual components because they all melted together in the magma.

We LOVED this activity. It is simple and yet it models the process so well!

Sebastian's illustration of the rock cycle

Metamorphic Rock Examples

As I pointed out with Igneous Rocks and Sedimentary Rocks, we are lucky to have easily accessible examples of all three kinds of rocks in our nearby canyons, so using this guide, we spent a day driving around and looking at these examples. We saw the metamorphic rocks quartzite and marble in Big Cottonwood Canyon.

The vertical layers in this quartzite are amazing. So linear and sheet-like!

This is lovely white marble from the Mississippian Period. We learned from an informational sign that because of the hardness and durability of this rock, this site (with marble on both sides of the road) has been considered for a dam in Big Cottonwood Canyon.

Metamorphic Rock activities

This is a great activity I saw all over on Pinterest---the Metamorphic Snickers Bar. You start with a Snickers Bar, representing a sedimentary rock. (You can see distinct layers, as well as inclusions like fossils.) Put the "rock" in a ziploc bag and add intense heat and pressure.

I had the children put a book on top of the bag (to distribute the pressure more evenly) and count to 30.

Your sedimentary rock has metamorphosed into a metamorphic rock! You can see the mineral components are basically the same, but they look totally different. This new "rock" exhibits foliation! And now you can eat it; yum!

Seb's drawing of his two "rocks"

Here's another way to demonstrate foliation and metamorphosis (via The Happy Scientist. As I've said before, his site is so great. He explains all this stuff way better than I do. Well worth the subscription price!). Make a bunch of different minerals and sediment by rolling little balls out of a few different colors of playdough. (I had each boy roll out several balls of one color, and then they traded around so everyone had some balls of each color.)

Group several balls together and add some gentle pressure, to make these minerals and sediments stay together in a consolidated "sedimentary rock." You can cut your rock gently in half with a butter knife to see how it looks in cross section.

Now press down on your sedimentary rock to simulate the heat and pressure created deep inside the earth.

Cut the rock in half again. Now you can see foliation of the minerals!

You can metamorphose the rock again to see more foliation and marbling! (Some metamorphic rocks metamorphose again into a new rock when even more pressure is added to them.)