Wk1_Module1B_EarthSpheres

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School

University of Cincinnati, Main Campus *

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Course

108

Subject

Geography

Date

Oct 30, 2023

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doc

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(Slide #1) Hello Class! This is Week 1, Module 1B. In this short module, I will introduce the concept of the FOUR GREAT EARTH REALMS – or SPHERES. Of course, we all know that the Earth is a SPHERE, right? But in studying Physical Geography, it is common to subdivide the EARTH into FOUR DISTINCT REALMS, each of which can be thought of as its own SPHERE, each one representing one of the Earth’s major categories of PHYSICAL SYSTEMS. Those four great Earth REALMS or SPHERES are the ATMOSPHERE, the LITHOSPHERE, the HYDROPSHERE, and the BIOSPHERE. (Slide #2) The ATMOSPHERE consists of the gaseous layer that surrounds the Earth. It contains all the elements of our air – elements that are vital for all life on earth: Oxygen, hydrogen, and nitrogen. It is in the ATMOSPHERE that our weather systems form, that winds circulate and precipitation develops. Second, we have the LITHOSPHERE. The WORD lithosphere comes from Greek, meaning literally, “Stone sphere.” The LITHOSPHERE is the outermost shell of the Earth, and quite literally the PLATFORM for human existence. When we talk about the LITHOSPHERE, this will include such things as continental plates, landforms, soils, rocks, and mountains. Third, we have the HYDROSPHERE. Again, this word comes from GREEK, and it literally means “Water sphere.” By “HYDROSPHERE,” we mean ALL the water on the Earth, which includes a LOT! Hydrosphere is partly the liquid envelope of the oceans, but it’s also the ice-sheets. It’s the surface water on our landmasses, which means all the river, lake, and stream systems. It’s the ground water, some of which lies deep under the ground. And it’s the snowpack which feeds the surface water systems. Fourth, is the BIOSPHERE. The BIOSPHERE includes all living organisms on Earth – plant, insect, bird, mammal, fish, etc. (Slide #3) Now even though it’s useful to think of these realms as four distinct SPHERES, we know they are not entirely separate, are they? Rather, they overlap. One way to envision the overlap among the spheres is to think of the Earth’s LIFE LAYER. We use this term to refer to the BIOSPHERE, as it interacts with the three other spheres. Most of the processes of HUMAN LIFE and HUMAN CULTURE on earth are contained in the LIFE LAYER. It includes the LOWER ATMOSPHERE, or that layer of the atmosphere that lies closest to the surface of the Earth, which includes the air we breathe, the weather that affects us, the layer we fly our planes in, and so on. It includes the UPPER HYDROSPHERE, or the top layer of the oceans, where we extract the ocean’s resources, sail our ocean vessels, and so on. It includes the UPPER LITHOSPHERE, or that upper layer of the surface of the Earth that we build our cities

on and grow our food and mine our natural resources and so on. This diagram gives you a good sense of just how much of our human existence, and indeed much of life on earth – utilizes this very narrow band of the LIFE LAYER. (Slide #4) But this narrow LIFE LAYER is subject to human change! In physical geography, we look at the role of human activity in impacting the processes that go on in the life layer. We will look at such things as pollution and loss of biodiversity. We’ll look at the extreme events that occur in our atmosphere and lithosphere, producing what we call “Natural disasters” and affecting human life. We’ll also continually keep in mind the role of human activity in CLIMATE CHANGE. To do that, we’ll learn more about the CARBON CYCLE, which refers to the process by which one very important element, vital for human life – namely CARBON – cycles through the four Earth SPHERES of the Atmosphere, Hydrosphere, Lithosphere, and Biosphere. Humans are in the process of arriving at a better understanding of the Carbon Cycle. We know that human activity GENERATES Carbon Dioxide. How? Simply put, we unlock Carbon from the LITHOSPEHRE when we extract and burn FOSSIL FUELS. But natural processes generate Carbon Dioxide, too. And natural processes also WITHDRAW Carbon Dioxide. We know that Carbon Dioxide plays a role in heating up our atmosphere and altering our climate, our HYDROSPHERE, and our BIOSPHERE. But exactly how that process works will require us to delve much more deeply into these issues. This is something we’ll come back to as the weeks progress. So that concludes this short module! Thanks for your attention!

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