Time for an adventure this week with Librarian Renée! This week’s Nature Discovery is part one of two featuring geology; let’s get the dirt on rocks!
There are many reasons to love Colorado – 300 days of sunshine, beautiful seasons, abundance of outdoor activities, wild places. But the BIGGEST thing – the inspiration for songs, the reason Colorado is called Colorado – those awe-inspiring Rocky Mountains and famous Flatirons! We like to hike and camp in them, ski and climb them. But what do we really know about them? Scientists who study rocks and their formations are called geologists. So grab your magnifying glasses nature lovers, today we are going to be geologists and get the dirt on rocks!
Our planet is a rocky planet! From our tallest mountains to the Earth’s crust, rocks are the building blocks of the Earth and minerals are the building blocks of rocks. Rocks are a naturally-occurring collection of one or more minerals. Minerals are inorganic (meaning not made from living material), crystalline solid substances that are found in the earth’s crust. A crystalline solid is a solid substance that has a highly organized, crystal structure. Salt is an example of a mineral. It is made up of two substances, Sodium and Chloride, that naturally form together to form a crystalline solid. Feldspar is another example of a mineral. It is commonly found in rock formations and is easily recognizable by its pink color.
Top:salt, bottom left: Feldspar, bottom right: Feldspar granite
Rocks can be made up of many different combinations of minerals, giving rocks their unique appearances, but there are only three types of rocks: igneous, metamorphic, and sedimentary. What determines the type of rock is how the rock is made.
Igneous rocks are formed deep inside the earth in pockets of hot, liquid magma. Magma is molten (or liquified) rock, suspended crystals, and gases. When this mixture cools and solidifies (becomes solid) quickly, in a geologic event such as a volcanic eruption or shifting of the earth’s crust, igneous rock is formed. Because it solidifies quickly, igneous rock has a more uniform appearance of its crystalline structures.
Metamorphic rocks are made deep inside the earth where it’s hot and where there is a lot of pressure, but not liquid magma. The heat and pressure transform the rock, much like when an insect goes through metamorphosis, hence the name metamorphic. Because of the pressure, crystalline structures form in layers or ribbons.
Sedimentary rocks are made on the earth’s surface by the process of weathering. Weathering is the breaking down of rocks by weather, such as wind and water. As rocks break down, or erode, from weathering, the rock sediment is deposited layer upon layer. Pressure builds as the sediment layers increase. With time and pressure, these layers become cemented together and a new sheet of sedimentary rock has been formed. Sedimentary rocks are made up of all three types of rocks.
When we look to the west and see our glorious snow-capped mountains, we are looking at metamorphic rock. When we hike along the foothills, we are hiking on sedimentary rock. The story of how they came to be there is just as fascinating and will be the focus of Geology part two; back to the future! Stay tuned!
In the meantime, check out this great book on Rocks and Minerals by DK books.
Until next time, Happy Adventures! -Renée