Chapter 2 Earth As a System 2.2 Energy in the Earth System EARTH & SPACE SCIENCE Chapter 2 Earth As a System 2.2 Energy in the Earth System

2.2 Energy in the Earth System Objectives Compare an open system with a closed system. List the characteristics of Earth’s four major spheres. Identify the two main sources of energy in the Earth system. Identify four major processes in which matter and energy cycle on Earth.

Introduction The different fields of Earth science have traditionally been studied separately. Oceanographers studied the ocean, geologists studied Earth’s rocks and interior, and meteorologists studied the atmosphere. The new approach to studying the Earth integrates many of the traditional fields and treats Earth as a system with many interacting, interdependent components.

Earth-System Science A system is an organized set of related, interacting parts (including organisms) that work together. Systems can be as small as an atom, or as vast as the universe. Systems have boundaries and often have matter and energy flowing through them. A large, complex system is the result of interrelated smaller systems.

Earth-System Science Matter is anything that takes up space and has mass. Energy is the ability to do work and can be transferred in a variety of ways. A system can be described by the way that energy flows into, out of, or through that system. Changes in chemical or physical properties are often signs of transfers of matter and energy in the Earth’s systems.

Earth-System Science Earth is a closed system with respect to matter because matter is neither being added to or taken away from Earth over time (meteorites and satellites not withstanding). Earth is an open system with respect to energy because Earth’s primary energy input is solar (from the sun). Energy is also released from the Earth in the form of light and heat (infrared radiation).

Earth’s Four Spheres The atmosphere is a blanket of gases that surrounds the Earth. Our atmosphere is made primarily of nitrogen – 78% and oxygen – 21% The troposphere, the lowest level of our atmosphere, is where most of the atoms are found and where weather occurs Water covers 71% of Earth’s surface area. About 97% of the water on Earth is in the oceans About 2/3 of the fresh water on Earth is frozen in glaciers

Earth’s Four Spheres The geosphere, the solid part of the Earth, includes all of the continents, ocean floor, and interior of the Earth. The biosphere includes all forms of life on Earth. Organic matter that has not decomposed is also included in the biosphere

Earth’s Energy Budget The first law of thermodynamics states that energy cannot be created or destroyed, it can only be transferred between systems. Matter, just like energy, can be transferred, but not created or destroyed. The second law of thermodynamics states that when energy transfer takes place, matter becomes more disorganized through time. As a result of the second law of thermodynamics, the universe’s energy is spread out more and more over time. Matter and energy are constantly being exchanged between the four spheres of Earth.

Earth’s Energy Budget Radioactive decay and gravitational attraction heated the Earth’s interior during its formation about 4.6 billion years ago. The amount of heat generated by radioactive decay in the Earth’s interior over time has declined. The decay of radioactive isotopes, along with leftover energy from the formation of the Earth, still keep the Earth’s interior hot. Due to temperature and density differences, materials in the interior of the Earth move about by convection.

Earth’s Energy Budget It is thought that convection drives tectonic plate motion which is responsible for the formation of ocean floors and mountains. The Earth’s most important external energy source is the sun. Wind and ocean currents, biogeochemical cycles, chemical reactions, weathering and erosion are all powered by the sun. Gravitational pull from the moon and sun, as well as the rotation of the Earth also have an impact on Earth systems.

Cycles in the Earth System A place where matter or energy is stored is called a reservoir. A cycle is a group of processes in which matter and energy repeatedly move through a series of reservoirs. Many elements on Earth cycle between reservoirs. The amount of time spent in a reservoir can be anywhere from hours to millions of years.

Cycles in the Earth System The nitrogen cycle. Nitrogen is a part of proteins Most living things cannot use atmospheric nitrogen (N2) Nitrogen must be fixed before it can be used by most living things Lightning can convert some atmospheric nitrogen into nitrates – a useable form Some nitrogen-fixing bacteria in the soil and in root nodules produce ammonia (NH3) Bacteria in soil and water add nitrogen back to the atmosphere

Cycles in the Earth System The carbon cycle. Carbon is an important element in all living things and serves as the basis for all organic compounds Carbon dioxide from the atmosphere is converted into carbohydrates in plants Other organisms eat plants and the carbon is transferred to their body When organisms (including plants) decay, some of the carbon is released as carbon dioxide back into the environment Carbon can also be stored in the form of fossil fuels or as individual fossils for a very long time.

Cycles in the Earth System The phosphorous cycle. Phosphorous, an essential element for some larger organic molecules, is rarely found in gaseous state Some animals excrete phosphorous in their waste Plants absorb phosphorus from soil and water via their roots Animals get their phosphorous by eating plants or animals that have eaten plants When animals and plants die, phosphorus is returned to the soil through decomposition

References Earth System - http://www.geo.arizona.edu/palynology/geos210/lec_02.html Nitrogen Cycle - http://www.ux1.eiu.edu/~cfruf/bio3002/nitrogen_cycle.htm Carbon Cycle - http://www.answers.com/topic/carbon-cycle Phosphorus Cycle - http://www.bio.miami.edu/dana/160/160S03_26.html