The Earth As A System

The Earth Is Unique Because It Is The Only Planet That: Has liquid water Has an atmosphere with oxygen Supports life

One reason that scientists study the characteristics of earth that support life is so that they can investigate other planets that may support life.

Earth Basics The earth is the 3rd planet from the sun. The earth formed about 4.6 billion years ago. About 71 percent of the earth is covered with water. The spinning earth is an oblate spheroid with a polar diameter of 40,007 km and a polar diameter of 40,074 km. The earth is relatively smooth when compared to other planets.

The earth’s interior cannot be studied directly but is analyzed with the use of seismic waves. Three compositional zones have been identified: The outermost layer of solid rock is the crust. It makes up less than one percent of the earth. It varies in thickness from only 5-10 km below the oceans and up to 15-80 km below the continents. The Mohorovicic Discontinuity or Moho marks the beginning of the mantle. The mantle is made up of heavy rock making up 2/3 of the earth’s mass and is 2900 km thick. The core at the center of the earth has a radius of about 3500 km and is made up mostly of iron and nickel.

The compositional model of the earth has been divided into five structural zones: Below the crust, the uppermost part of the mantle is cool and brittle. This earth zone is called the lithosphere. Below the lithosphere in the upper mantle is the less rigid asthenosphere which is 200-250 km thick and has the ability to flow like plastic. The solid rock below the asthenosphere is called the mesosphere. At a depth of 2,900 km the liquid outer core begins and extends to 5,150 km where the solid inner core begins.

The movements in the earth’s core generate a huge magnetic field around the earth that reaches far into space. This magnetosphere concentrates into two magnetic poles on the earth’s surface.

The Earth, like all bodies in the universe is affected by gravity The Earth, like all bodies in the universe is affected by gravity. Newton’s Law of Gravitation gives us the ability to describe this universal force.

The force of attraction that the earth exerts on all objects is called weight. Weight is determined by the amount of mass in an object. Weight varies with an object’s location on the earth because the earth is not a perfect sphere.

Energy In The Earth System

Section 2 Earth System Science

An organized group of related objects, components, or subsystems that interact to create a whole is a system.

The function of any system depends on the organization of its matter and the flow of its energy.

A closed earth system is one in which matter is not exchanged with the surroundings.

In an open earth system, both matter and energy may be exchanged with the environment.

Technically, all of the systems that make up the Earth are open Technically, all of the systems that make up the Earth are open. But the Earth system itself is closed. Very little matter is exchanged with space.

The matter on the earth is divided into 4 spheres. Atmosphere Hydrosphere Geosphere Biosphere

Exchanges of energy on earth follow two strict laws: The First Law of Thermodynamics - Energy is neither created nor destroyed but simply changes forms. The Second Law of Thermodynamics - Matter becomes less organized over time.

The energy that drives the geology of the earth comes from 3 sources within the earth Radioactive decay Gravitational contraction Heat left over from the formation of the earth.

Interacting systems at the earth’s surface receive their energy from the sun.

The Earth system contains a number of biochemical cycles in which vital energy and matter is moved between reservoirs over a period of hours to millions of years.

Four main biochemical cycles include the: Nitrogen cycle Carbon cycle Phosphorus cycle Water cycle

Phosphorus enters the soil and water when rock breaks down Phosphorus enters the soil and water when rock breaks down. It is then absorbed by plants and cycled through animals with decomposition.

All of the natural cycles can be affected by human activities.

Ecology The study of the complex relationships between living things and their environment.

The earth’s environment is studied by dividing it up into smaller environments called ecosystems. Each ecosystem consists of a community of living things together with a nonliving environment.

Ecosystems are often studied by the way that they cycle food: Producers – Green plants that make their own food by using energy from the sun. Consumers – Animals that feed on producers and other consumers. Decomposers – Bacteria and fungi that break down detritus to make nutrients available to plants again.

Each environment can only support a given number of organisms and still cycle matter and transfer energy efficiently. This maximum number of organisms is called the carrying capacity.

After a disturbance, ecosystems are able to restore the balance of nature again over time. If the physical factors of the environment are not permanently changed, ecosystems can restore themselves to their original state.

One should remember that nutrients are cycled as they move through the complicated food web of an ecosystem but energy is lost to heat as it passes through the system and cannot be reused.

It is each person’s responsibility to be a steward of the environment It is each person’s responsibility to be a steward of the environment. We need fertile soils, clean air, and water to live in our biosphere. Overconsumption and pollution can destroy these balances. It is a constant task to care for our environmental home.