This earthcache is located at The Boulder Garden which is located in the center of the parking circle near the Harris Nature Center building. The Nature Center is open Monday - Saturday 9 to 4pm and Sundays 12 to 4pm.
You will be learning about these groups of boulders which fall into three major categories: igneous, sedimentary, and metamorphic. Hopefully, you will be able to identify the different types more easily in your other adventures.
There are 3 types of rocks:
Metamorphic Rocks: derived from the word “Metamorphism” which means change. This is the oldest type of rock in the Michigan Basin, first dates back 3.5 billion years ago during the Archean time division. Metamorphic Rocks are formed when existing rocks are changed by heat, extreme pressure and chemical processes usually while buried deep in the Earth’s surface, causing a chemical or physical change to form the new rock. This rock is broken down into several categories: Iron Ore, Saturolite, Schist, Slate, Quartzite, Marble and Gneiss. It can be identified often by the coloring, it could be light or dark in color with opposite toned bands through the rock.
Igneous Rocks: derived from the Latin word “Ignis” meaning fire. This rock first dates back about 2.5 billion years, also during the Archean time division. Igneous rock was formed from cooling magma, molten rock and surface lava. When identifying these rocks you will see that they have shiny flecks throughout the rock coloring. This is because of the silica that is a big part of the magma when this type of rock was formed. Intrusive Igneous Rocks (Plutonic) crystalize below the Earth’s surface and cool slowly which forms large crystals. Extrusive Igneous Rocks (Volcanic) erupt to the Earth’s surface and cool quickly which forms small crystals. This rock is broken down into several categories: Granite, Granodiorite, Pigmatite, Basalt and Rhyolite. These rocks have many colors and textures due to different minerals. The Earth’s upper crust is 95% Igneous Rock.
Sedimentary Rocks: This rock is much younger than the other two types of rock. It dates back about 3.5 million years ago during the late Devonian period and the Mississippian time division. It formed when sediment such as minerals and organic matter settled in place. These sediments are cemented together and compacted over time and are often deposited in layers that frequently contain fossils. Sedimentary Rocks form at or near the Earth’s surface but are only a small percentage of the Earth’s crust. Sedimentary rock is broken down into several categories: Sandstone, Shale, Limestone, Halite and Gypsum. These types of rock come in many colors and textures including rocks that you can see smaller rocks imbedded in them.
At the posted coordinates you will find four signs in front of a collection of boulders that tell the story of this collection. This is where your work begins. To claim this cache you will need to answer these questions according to the signs and send me your answers, DO NOT post your answers. The only log you will be posting is your adventure and photos that are NOT spoilers.
1) From what category is granite classified?
2) What is the reason for the different sized crystals that are formed in igneous rocks?
3) What is Jasper Conglomerate also known as?
4) What causes the different colored bands in the Gneiss boulder?
5) Use the Sedimentary Rock sign to identify the sandstone and limestone boulders.. List two differences you notice between sandstone and limestone.
This Earthcache has been placed with permission of the Harris Nature Center