Earth as a System

Chapter 2

• Earth Facts:– the third planet from the sun in

our solar system– formed about 4.6 billion years ago – made mostly of rock.– Approximately 70% of Earth’s

surface is covered by a – Earth is an oblate sphere– Pole-to-pole circumference is

40,007 km. – Equatorial circumference is

40,074 km.– Average diameter is 12,756 km.

• Seismic waves – waves that travel through Earth; they are caused by earthquakes and by explosions near Earth’s surface.

• Important discoveries have been made about Earth’s interior through studies of seismic waves

3 Major Compositional Zone:– Crust– Mantle– Core

5 Major Structural Zones:– Lithosphere– Asthenosphere– Mesosphere– Liquid Outer Core– Solid Inner Core

Layers of Earth

Compositional Zones of Earth’s Interior

• Crust - thin and solid outermost layer, lies above the mantle

• Oceanic crust - lies under the oceans, is only 5 to 10 km thick. (3-5 mi)

• Continental crust varies in thickness from 15 km to 80 km. (avg 25 mi)

• Mantle - layer of rock that lies between Earth’s crust and core– is nearly 2,900 km thick and makes up almost

two-thirds of earth

• Core - the central part of Earth that lies below the mantle– a sphere composed mainly of nickel and iron

whose radius is about 3,500 km

• The crust is composed of two types of rock.– The continental crust is mostly granite. – The oceanic crust is basalt. Basalt is much

denser than the granite.

• Because of this the less dense continents ride on the denser oceanic plates.

Structural Zones of Earth’s Interior

• Lithosphere - solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle– between 15km and 300 km thick.

• Asthenosphere - solid layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it– about 200 km thick

Convection Currents

• The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over.

Convection Currents The next time you heat

anything like soup or water in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the asthenosphere they also move the crust. The crust gets a free ride with these currents, like the cork in this illustration.

Safety Caution: Don’t get your face too close to the boiling water!

• Mesosphere - strong, lower part of the mantle between the asthenosphere and the outer core– reaches from the bottom of the

asthenosphere to a depth of about 2,900 km.

• Liquid outer core -below the mesosphere surrounds the solid inner core

• Solid inner core - begins at a depth of 5,150 km, composed of nickel and iron

Outer Core

• The core of the Earth is like a ball of very hot metals. The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the melted metals of nickel and iron.

Earth’s Interior

Core

• The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid.

Layers of Earth

Earth as a Magnet• Magnetosphere - extends beyond

the atmosphere • Where the magnetic field balances the

pressure of the solar wind – 63,000 km

• Scientists think that motions within the liquid iron of Earth’s outer core produce electric currents that in turn create Earth’s magnetic field.

Magnetosphere

Earth’s Gravity

• Gravity - the force of attraction that exists between all matter in the universe

• Newton’s law of gravitation - the force of attraction between any two objects depends on the masses of the objects and the distance between the objects

• The larger the masses of two objects are and the closer together the objects are, the greater the force of gravity between the objects will be.

• Weight - measure of the strength of the pull of gravity on an object

• An object’s weight depends on its mass and its distance from Earth’s center

Weight and Location

• Because the distance between Earth’s surface and its center is greater at the equator than at the poles, the weight of an object at the equator is about 0.3% less than its weight at the North Pole

• Matter - anything that has mass and takes up space.

• Energy - the ability to do work. Energy can be transferred in a variety of forms, including heat, light, vibrations, or electromagnetic waves.

Closed Systems• system in which energy, but not matter is

exchanged with the surroundings.

Open Systems• system in which both energy and matter

are exchanged with the surroundings

The Earth system is almost a closed system because matter exchange is limited

Energy enters the system in the form of sunlight and is released into space as heat.

Only a small amount of dust and rock enters, and only a fraction of the hydrogen atoms in the atmosphere escape into space.

4 Spheres of Earth:• Atmosphere• Hydrosphere• Geosphere• Biosphere

• Atmosphere - mixture of gases that surrounds a planet or moon– The atmosphere provides the air you

breathe and shields Earth from the sun’s harmful radiation

• Hydrosphere - portion of Earth that is water– Water covers 71% of Earth’s surface.– occur in the form of oceans, lakes, rivers,

streams, glaciers and ice sheets, and groundwater.

• Geosphere - the mostly solid, rocky part of Earth; extends from the center of the core to the surface of the crust– all of the rock and soil on the surface of

the continents and on the ocean floor.– also includes the solid and molten interior

of Earth.

• Biosphere - part of Earth where life exists; includes all of the living organisms– composed of all of the forms of life in the

geosphere, in the hydrosphere, and in the atmosphere, as well as any organic matter that has not decomposed.

– The biosphere extends from the deepest parts of the ocean to the atmosphere a few kilometers above Earth’s surface.

Earth’s Energy Budget

• Ecology - the study of the relationships between living things and their nonliving, or abiotic environment.

• Ecosystem - a community of organisms and their abiotic environment– An ecosystem may be as large as an

ocean or as small as a rotting log. The largest ecosystem is the entire biosphere.

• Producers - organisms that make their own food, most producers use energy from the sun to produce their own food

• Consumers -organisms that get their energy by eating other organisms.

• Decomposers – a consumer that get energy by breaking down dead organisms

• To remain healthy, an ecosystem needs to have a balance of producers, consumers, and decomposers

Concentration of Plant Life on Earth