EARTH SCIENCECHAPTER 2 EARTH AS A SYSTEM

Earth a Unique Planet

OBJECTIVES:• Describe the size and shape of the Earth.• Describe the compositional and structural layers of Earth’s

surface.• Identify the possible source of Earth’s magnetic field.• Summarize Newton’s law of gravitation.

KEY TERMS:crust, mantle, core, lithosphere, asthenosphere, mesosphere

Earth BasicsEarth…• is the third planet from the sun in our solar system.• formed about 4.6 billion years ago.• is made mostly of rock.• approximately 70% of the surface is covered

by water, global ocean.• is an oblate spheroid, has a slightly flattened

shape.

Earth’s InteriorDirect observations of the Earth’s interior has been limited to the upper few kilometers that can be reached by drilling.

Scientists rely on indirect methods to study the Earth at greater depths. Scientists have made important discoveries about the Earth’s interior through the studies of seismic waves. Seismic waves are vibrations that travel through the Earth.

By studying these seismic waves, scientists have determined that the Earth is made up of three major compositional zones and five major structural zones.

Earth’s Interior

CompositionalZones

Core

Mantle

Crust

Crust

Mantle

Continental crust

Oceaniccrust

Ocean

Moho

Structural Zones

Lithosphere

Asthenosphere

Mesosphere

Outer Core(liquid)

Inner Core(solid)

Lithosphere

Asthenosphere

Earth’s InteriorCrust

• Thin, solid outermost zone of the Earth• Makes up 1% of the Earth’s mass.• The crust beneath the oceans is called oceanic crust, and is

only about 5-10km thick.• The crust that makes up the continents is called

continental crust, and ranges in thickness from 15-80km.• The lower boundary of the crust is called the Mohorovicic

discontinuity, or Moho.

Earth’s InteriorMantle

• Layer that underlies the crust, and is more dense.• Makes up 67% of the Earth’s mass.• The mantle is nearly 2900km thick.

The mantle can be divided into three layers:1. Lithosphere – the transition between the crust

and the mantle. Rigid layer 15 to 300km thick.2. Asthenosphere – less rigid layer about 200km thick, because of the enormous

heat and pressure, this rock has the ability to flow. The ability of solid rock to flow is called, plasticity.

3. Mesosphere - stronger, lower part of the mantle that extends to the Earth’s core.

Earth’s InteriorCore

• The center of the Earth.• Spherical shaped with a radius of 3500km.• Composed mainly of iron and nickel.• The temperature of the core is estimated to be about 5500oC

(almost equal to the temp of the Sun)

Two parts of the core:

1. Outer Core – High temperature, very dense molten metal iron and nickel.

2. Inner Core – Dense rigid solid.

Earth as a MagnetThe Earth has two magnetic poles. The lines of force of Earth’s magnetic field extend between the North geomagnetic pole and the South geomagnetic pole.

The Earth’s magnetic field, extends beyond the atmosphere and affects a region of space called the magnetosphere.

Earth as a MagnetThe source of the magnetic field may be the liquid iron in the Earth’s core. Scientists hypothesize that motions within the core produce electric currents that in turn create the Earth’s magnetic field.

However the sun and moon both have a magnetic field…yet the sun has no iron and the moon has no liquid core?

Earth’s GravityEarth, like all objects in the universe, is affected by gravity. Gravity is the force of attraction that exists between all objects in the universe.

The 17th century scientist, Sir Isaac Newton was the first to explain the phenomenon of gravity.

Law of GravitationThe force of attraction between any two objects depends on the masses of the objects and the distance between the objects.

Weight and MassEarth exerts a gravitational force that pulls all objects toward the center of the Earth. Weight is a measure of the strength of the pull of gravity on an object.

The newton (N) is the unit used to measure weight.

1 Newton (N) = 1kg x m/s/s

The force of attraction of gravity on the Earth is 9.8m/s/s or 9.8m/s2

The mass of an object does not change with location.The weight of an object does change with location.

THE SCALE OF THE UNIVERSE

Section 1 Review1. Describe the size and shape of the Earth.2. Describe two characteristics that make the Earth unique in our solar system.3. Summarize how scientists learn about Earth’s interior.4. Compare Earth’s compositional layers with its structural layers.5. Identify the possible source of Earth’s magnetic field.6. Summarize Newton’s law of gravitation.7. Making Inferences. What does the difference between your weight at the

equator and your weight at the poles suggest about the shape of the Earth?8. Making Comparisons. How does the asthenosphere differ from the

mesosphere?9. Analyzing Ideas. Why would you weigh less on a high mountain peak than

you would at sea level?

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 processes in which matter and energy cycle on Earth.

KEY TERMS:system, atmosphere, hydrosphere, geosphere, biosphere

Earth-System ScienceA system is an organized group of related objects or components that interact to create a whole.

• Systems can be small – subatomic• Systems can be large – universe• All systems have boundaries• Many system have matter and energy that flow through them.• Even though systems can be described separately – all systems are linked.

The operation of the Earth system is a result of the two most basic components of the universe:

• Matter – anything that has mass and takes up space.• Energy – the ability to do work.

A system can be described by the way that matter and energy are transferred within the system or to and from other systems.

Earth-System ScienceCLOSED SYSTEM

A closed system is a system in which energy, but not matter, is exchanged with the surroundings.

What would be some examples of a closedsystem:

• Egg• Aquarium• Greenhouse• Sun Tea

CLOSED SYSTEMENERGY IN ENERGY OUT

Earth-System ScienceOPEN SYSTEM

An open system is a system in which both energy and matter are exchanged with the surroundings.

What would be some examples of an opensystem:• Boiling pot of water• Ocean• Your body

OPEN SYSTEMENERGY IN ENERGY OUT

MATTER OUT

MATTER IN

Earth-System ScienceTHE EARTH SYSTEM

Technically, all systems that make up the Earth systems are open. But the Earth System is almost a closed system because matter exchange is very limited.

• Energy enters the system in the form of sunlight.• Energy is released to space as heat.• Only a small amount of dust and rock from space enters the system.• Only a fraction of hydrogen atoms in the atmosphere escape into space.

Earth’s Four Spheres

BIOSPHERE

GEOSPHERE

HYDROSPHERE

ATMOSPHERE

Earth’s Four Spheres THE ATMOSPHERE

The atmosphere is the blanket of gases that surrounds Earth’s surface.• Provides the air that we breathe• Shields the Earth from the sun’s harmful rays• Atmospheric composition:• 78% Nitrogen• 21% Oxygen• 1% other gases…argon, carbon dioxide, water vapor, and helium.

Earth’s Four Spheres THE HYDROSPHERE

The hydrosphere is all of the Earth’s water except the water that is gaseous form in the atmosphere.• Water covers 71% of the Earth’s surface area.• 97.5% of surface water is contained in the salty oceans.• Fresh water (2.5%) is found• Swamps, Lakes, ponds, rivers and streams (0.3%)• Underground in soil and bedrock (30.8%)• Frozen in glaciers and the polar ice sheets (68.9%)

Earth’s Four Spheres THE GEOSPHERE

The geosphere is the solid Earth including the continental crust and the oceanic crust and everything beneath.• All of the rock and soil on the surface of the continents and the ocean floor.• The solid and molten interior of Earth• Processes that brings matter from the inside of the earth to the surface• Processes that moves surface matter back into the Earth’s interior.

Earth’s Four Spheres THE BIOSPHERE

The biosphere is composed of all of the forms of life in the geosphere, in the hydrosphere, and the atmosphere.• It also includes any organic matter that has not decomposed.• Once organic matter has decomposed it becomes a part of the other three spheres• Extends from the deepest part of the ocean to a few kilometers above the Earth.

Earth’s Energy Budget Exchanges and flow of energy on Earth happen in predictable ways. The flow of incoming and outgoing energy is known as the Earth’s Energy Budget.

According to the First Law of Thermodynamics, energy is transferred between systems, but it cannot be created or destroyed.

The Second Law of Thermodynamics states that when energy transfer takes place, matter becomes less organized with time. This means that the universe’s energy is spread out more and more over time.

100% incoming solar radiation

30% reflected to space

19% absorbed by the atmosphere

51% absorbed by water and

land

70% reradiated as longwave

radiation

6% scattered by air

20% reflected by clouds

4% reflected by water and land

3% absorbed by clouds

16% absorbed by water vapor, dust, ozone and carbon

dioxide

Earth’s Energy Budget

Earth’s Energy Budget Matter and energy are constantly being exchanged between the spheres. Thus constant exchanges happen through:• Chemical reactions• Radioactive decay• Radiation of energy (including light and heat)• Growth and decay of organisms

100% incoming solar radiation

30% reflected to space

19% absorbed by the atmosphere

51% absorbed by water and

land

70% reradiated as longwave

radiation

6% scattered by air

20% reflected by clouds

4% reflected by water and land

3% absorbed by clouds

16% absorbed by water vapor, dust, ozone and carbon

dioxide

Earth’s Energy Budget

Earth’s Energy BudgetInternal Sources of Energy

Because Earth’s interior is warmer than its surface layers, hot materials move toward the surface in a process called convection.

As the hotter material rises the cooler, denser material sinks. This continuous rising and sinking of earthen material is known as a convection cell.

This process drives the motion in the surface layers of the geosphere that creates mountain ranges ocean basins.

Earth’s Energy Budget

Earth’s Energy BudgetExternal Sources of Energy

The most important external energy source is the sun.

Solar radiation warms the Earth’s atmosphere and surface. This heating is responsible for:• Movement of air masses, generating winds and ocean

currents• Fueling the growth of plants• Providing food for animals to feed• Chemical reactions that break down rock into soil

The moon and the sun’s gravitational pull combined with the Earth’s rotation, generates the tides that causes currents and drive the mixing of ocean water.

Earth’s Energy Budget

Cycles in the EarthTHE NITROGEN CYCLE

Organisms on Earth use the element Nitrogen to build proteins, which are used to build cells. Nitrogen gas makes up 78% of the atmosphere, but most organisms cannot us the atmospheric form of nitrogen. The nitrogen must be altered, or fixed, before organisms can use it. Nitrogen fixing is an important step in the nitrogen cycle.

Earth’s Energy Budget

Cycles in the EarthTHE NITROGEN CYCLE In the nitrogen cycle, nitrogen moves from air to soil, from soil to plants and animals, and back to the air again.

Nitrogen is removed from the air by nitrogen fixing bacteria. These bacteria chemically change nitrogen in the air to nitrogen compounds which are vital to the growth of all plants.

When animals eat the plants, the nitrogen becomes a part of the animals bodies.

These compounds are returned to the soil by the decay of dead animals and in the animals’ excretions. Earth’s Energy Budget

Cycles in the EarthTHE CARBON CYCLE

Carbon is an essential substance in the fuels used for life processes. Carbon moves through all four spheres in process called the carbon cycle.

Part of the carbon cycle is a short-term cycle, plants convert carbon dioxide, CO2, from the atmosphere into carbohydrates, such as glucose, C6H12O6. Then organisms eat the plants and obtain the carbon from the carbohydrates.

Earth’s Energy Budget

Next, organisms’ bodies break down the carbohydrates and release the carbon back into the air as CO2. Organisms also release carbon into the air through decay as CO2 or waste as methane, CH4.

Cycles in the EarthTHE CARBON CYCLE

Part of the carbon cycle is a long-term cycle in which carbon moves through Earth’s four spheres over a very long period time.

Carbon is stored in the geosphere in buried plant and animal remains, and in a type of rock called carbonate. Carbonate forms from shells and bones of once-living organisms.

Cycles in the EarthTHE PHOSPHORUS CYCLE

The element phosphorus is part of some molecule that organisms need to build cells. During the phosphorus cycle, phosphorus moves through every sphere, except the atmosphere, because phosphorus is rarely a gas.

Phosphorus enters the soil and water when rock breaks down and when phosphorus dissolves in water.

Organisms excrete the excess phosphorus in their waste and this phosphorus may enter soil and water. Plants absorb the phosphorus through their roots, where they incorporate the phosphorus into their tissues.

Animals absorb the phosphorus when they eat the plants, and when the animals die the phosphorus returns to the environment through decomposition.

Cycles in the EarthTHE WATER CYCLE

The movement of water from the atmosphere to Earth’s surface and back to the Earth’s surface is always taking place. This continuous movement is called the water cycle.

In the water cycle, water changes from liquid water to water vapor through the energy transfers involved in evaporation and transpiration

Evaporation occurs when energy is absorbed by liquid water and the energy changes the water into water vapor. Transpiration is the release of moisture from plant leaves.

During these processes, water absorbs heat and changes state. When water loses energy it condenses to form water droplets, such as those that form clouds. Eventually, water falls back to Earth’s surface as precipitation, such as rain, snow, or hail.

Section 2 Review1. Explain how the Earth can be considered a system.2. Compare an open system with a closed system.3. List two characteristics of each of Earth’s four major spheres.4. Identify the two main sources of energy in Earth’s system.5. Identify four processes in which matter and energy cycle on Earth6. Explain how carbon cycles in Earth’s system.7. Explain how nitrogen cycles in Earth’s system.8. Identifying Relationships. For each of Earth’s four spheres, describe one way that the water

cycle affects the sphere.9. Determining Cause and Effect. What effect, if any, would you expect a massive forest fire to

have on the amount of carbon dioxide in the atmosphere? Explain your answer.10. Analyzing Ideas. Early Earth was constantly being bombarded by meteorites, comets, and

asteroids. Was early Earth an open system or a closed system? Explain your answer?11. Analyzing Relationships. Explain the role of energy in the carbon cycle.

Ecology

OBJECTIVES:• Define ecosystem.• Identify three factors that control the balance of an ecosystem.• Summarize how energy is transferred through an ecosystem.• Describe one way that ecosystems respond to environmental

change.

KEY TERMS:ecosystem, carrying capacity, food web

EcosystemECOSYSTEMS

A community of organisms and the environment that the organisms inhabit is called an ecosystem. The terms ecology and ecosystem come from the Greek word oikos which means “house”.

Ecosystems…• May be as large as an ocean• May be as small as a rotting log.• The largest ecosystem is the entire biosphere.• Only a fraction of hydrogen atoms in the atmosphere escape into space.

EcosystemECOSYSTEMS

Most Earth’s ecosystems contain a variety of plants and animals.

To remain healthy, an ecosystem needs to have a balance of :• Producers are organisms that make their own food. (Plants) • Consumers are organisms that get their energy by eating other organisms

(producers or other consumers)• Decomposers are organisms that get their energy by breaking down dead

organisms.

Producer / Consumer / Decomposer Game

Balancing Forces in EcosystemsECOLOGICAL RESPONSES TO CHANGE

Organisms in an ecosystem use matter and energy.

Because amounts of matter and energy in an ecosystem are limited, population growth that an environment can support at any given time is called the carrying capacity.

Changes in any one part of an ecosystem may affect the entire system in an unpredictable way. However, in general, ecosystems react to changes in ways that maintain or restore balance in the ecosystem. Ecosystems are resilient and tend to restore a community of organisms to its original state.

Balancing Forces in EcosystemsECOSYSTEMS

Organisms in an ecosystem use matter and energy.

Because amounts of matter and energy in an ecosystem are limited, population growth that an environment can support at any given time is called the carrying capacity.

Changes in any one part of an ecosystem may affect the entire system in an unpredictable way. However, in general, ecosystems react to changes in ways that maintain or restore balance in the ecosystem. Ecosystems are resilient and tend to restore a community of organisms to its original state.

MT. ST HELENS

1984 2013

Balancing Forces in EcosystemsENERGY TRANSFER

The ultimate source of energy for almost every ecosystem is the sun.

Plants capture solar energy by a chemical process photosynthesis.

This captured energy flows through ecosystems from plants, to the animals that feed on them, and finally to the decomposers of animal and plant remains. Matter also cycles through an ecosystem by this process.

Balancing Forces in EcosystemsENERGY PYRAMID

Balancing Forces in EcosystemsFOOD CHAINS & FOOD WEBS

The sequence in which organisms consume other organisms can be represented by a food chain.

However, ecosystems are complex and generally contain more organisms than are on a single food chain. In addition, many organisms eat more than just one other species, Therefore a food web is used to represent the relationships between multiple food chains.

Human Stewardship of the EnvironmentAll of the Earth’s systems are interconnected and changes in one system may affect the operation of other systems.

Ecological balances can be disrupted by human activity. Populations of plants and animals can be destroyed through overconsumption of resources.

• When humans convert large natural areas to agricultural or urban areas, natural ecosystems are often destroyed.

• Another serious threat to ecosystems is pollution. Pollution is the contamination of the environment with harmful waste products or impurities.

When people strive to prevent ecological damage to an area, they are trying to be responsible stewards of the Earth. To help ensure the ongoing health and productivity of the Earth system, many people work to use Earth’s resources wisely.

Section 3 Review1. Define ecosystem.2. Explain why the entire biosphere is an ecosystem.3. Identify three factors that control the balance of an ecosystem.4. Summarize how energy is transferred between the sun and the consumers in an ecosystem.5. Describe one way that ecosystems respond to environmental change.6. Compare a food chain to a food web.7. Summarize the importance of good stewardship of Earth’s resources.8. Making Inferences. Discuss two ways that the expansion of urban areas might be harmful

to nearby ecosystems.9. Analyzing Ideas. Why would adapting to a gradual change in environment be easier for an

ecosystem than adapting to a sudden disturbance be?.10. Making Inferences. Why does energy flow in only one direction in a given food chain of an

ecosystem.