Key Principles: Systems
Throughout the semester, we will try to learn about Earth processes by focusing in on a few key principles from which we can deduce other more complex ideas. To start off the semester, here are a few that I want you to think about. These are good starting points for many of the ideas that we will explore throughout the semester.
Earth is a System –
Most Earth scientists don’t study then entire Earth. As we learned in the beginning of this lecture, most Earth scientists study a part of the Earth based upon the different Earth spheres. Within these spheres are major Earth Cycles. Scientists use simple input-output models to monitor the changes in these different Earth cycles.
The Hydrosphere, the part of the Earth which is described by the stocks and movement of water, is generally studied by looking at the movement of water through the Hydrologic Cycle. Take a look at Figure 13.3 in your textbook. The red arrows show processes that remove water from the Earth’s surface and into the atmosphere. The blue arrows show processes that remove water from the atmosphere and shows how water interacts with the Earth’s surface. The brown arrows show processes that remove water from the Earth’s surface and into the ground. Think of these processes as arrows in an input-output analysis. These processes are named below in the table.
To help you to imagine this process, sit back, relax, turn the volume up on your speakers and watch the video below. The narrator has a smooth voice, so try not to get too sleepy!
The Lithosphere, the part of the Earth which is described by the stocks and movements of rocks and minerals, is generally studied by looking at the movement of rocks and minerals through the Rock Cycle. Take a look at Figure 3.13 in your textbook. Here you see three major rock types: igneous, sedimentary, and metamorphic rocks. These three different categories of rock, specifically, sedimentary rocks, were what got James Hutton thinking about how rock structures formed; and while he didn’t quite have the measurements to support his idea, he had hypothesized that rocks moved through this “great geologic cycle,” which we now call the Rock Cycle. It is a cycle because rocks are constantly being formed and destroyed.
Okay, so back to that figure: You can see the processes that define and form each different type of rock. The teal arrow at the top shows how sediments can form to become sedimentary rock. The orange arrow on the right shows how sedimentary rocks can be changed into metamorphic rock. That sedimentary rock can also undergo further destruction and be turned back into little bits of rock (or sediments). The red arrow shows that rock can be melted (from the heat within the Earth). And the dark blue arrows show that rock can be broken down into little bits of rock (or sediments). Sediments can also mix with “life” as the figure caption states. When this happens, we get soil. Soil is made up of little bits of rocks mixed with water and organic material. But we’ll cover that in the Soils module. See the table below.
