| << Chapter < Page | Chapter >> Page > |
The fourth layer, the thermosphere, extends outward from about 85 kilometers to about 600 kilometers. Its upper boundary is ill defined. The temperature in thethermosphere increases with altitude, up to 1500º C or more. The high temperatures are the result of absorption of intense solar radiation by thelast remaining oxygen molecules. The temperature can vary substantially depending upon the level of solar activity.
The lower region of the thermosphere (up to about 550 kilometers) is also known as the ionosphere. Because of the high temperatures in this region, gasparticles become ionized. The ionosphere is important because it reflects radio waves from the earth's surface, allowing long-distance radio communication. Thevisual atmospheric phenomenon known as the northern lights also occurs in this region. The outer region of the atmosphere is known as the exosphere. Theexosphere represents the final transition between the atmosphere and interplanetary space. It extends about 1000 kilometers and contains mainly helium and hydrogen. Most satellites operate in this region.
Concept: the earth is a system
Text from Open Source Earth Science Course
While studying the parts of the Earth System it is important to look for the emergent properties of the Earth System. How do the parts of the Earth Systemcome together to form a sum that is greater than the sum of its parts? This question is best answered by focusing on the Earth’s matter, energy, andlife.
A system has two distinguishing characteristics. The first is that it has SYNERGY. Synergy means that the whole is greater than the sum of the parts.This sounds a lot more complicated than it is. What it means is that when all of the pieces of a system are put together they are more valuable than all ofthe pieces would be if they were considered separately. A home is a good example. If you were to lay all the pieces and parts of your home in a pile youwould have a big pile of wood, insulation, pipes, wires, drywall, etc. Your pile of “house stuff” would be worth something but not nearly asmuch as your home is worth when all the “house stuff” is organized into a system.
The second distinguishing characteristic of a system is that it has EMERGENT PROPERTIES. Emergent properties are properties that emerge as a result of howthe system works together; properties that do not exist without the system. In other words, emergent properties are characteristics that are unique to thesystem as a whole. Let us consider the example of your home once again. Some emergent properties of your home may be its comfort and its safety. The comfortof your home is a function of the materials used to build it, the architectural design, and the furniture inside. The home’s safety is a propertydependent on the design, the strength and location of its doors and windows, and the neighbourhood in which it was built. Both the safety and comfort ofyour home are properties of the home that are a result of the “home system”; they are not dependent on just one aspect of the home.
Text from Earth as a System. " Teachers' Domain. 17 Dec. 2005. Web. 15 Oct. 2011.http://www.teachersdomain.org/resource/ess05.sci.ess.earthsys.hologlobe/”
Understanding our planet as an integrated system of components and processes is a fundamental part of Earth and space science research. Just as the human bodyis composed of interrelated systems that control specific bodily functions, Earth's four principal components — the atmosphere (air), lithosphere(land), hydrosphere (water), and biosphere (life) — perform critical roles that, together, support and sustain life on the planet.
Nothing influences the subsystems that contribute to Earth's dynamic behaviour more than heat. Heat comes from two sources: solar energy and radioactivity inthe Earth's core. Because of the angle at which the Sun strikes Earth, Earth's surface is heated unevenly. This creates Earth's three major climate zones— tropical, temperate, and polar — which then influence what types of life flourish in different locations.
The uneven heating also controls weather systems. The heat absorbed by the oceans and carried by its currents is constantly being released into theatmosphere. This heat and moisture drive atmospheric circulation and set weather patterns in motion. The weather patterns then influence vegetation, aswell as erosion and sediment transport.
The other heat source, deep within Earth's core, is responsible for plate tectonics, which gives the Earth its physical character: mountain ranges andvalleys, ocean basins and lake beds, and islands and trenches. The heat from Earth's core generates convection cells within its mantle, which help driveplate activity.
Ever since the first photos were sent back from space, our view of Earth has changed. Remote sensing instruments, such as satellites, allow us to betterunderstand the interrelationships between the different subsystems. For instance, recordings made by remote and Earth-based instruments show thatsignificant surface warming has occurred over the past three decades. Knowing this, scientists are working to determine how this will affect — andalready is affecting — the entire Earth system.
Possible slide-shows:
http://www.slideshare.net/Alyssa10/earth-science-biosphere-ppt
http://www.slideshare.net/shoreyl/3-biosphere
Video: The Earth as a System: http://www.oercommons.org/courses/earth-as-a-system/view
Questions
What are the parts of Earth’s System?
What are the properties of the Earth’s System?
How is the Earth’s System part of a larger system?
Notification Switch
Would you like to follow the 'Siyavula: life sciences grade 10' conversation and receive update notifications?
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|