Chapter 1 Objectives This is the introductory chapter. After reading this chapter you should be able to: 1. Identify the four spheres of Earth 2. Describe.

Chapter 1 ObjectivesChapter 1 Objectives• This is the introductory chapter. After reading this chapter you

should be able to:• 1. Identify the four spheres of Earth• 2. Describe the composition of each sphere.• 3. List forms of interaction between spheres.• 4. Define a system• 5. Describe the types and rates of changes.• 6. Describe the scientific method.• 7. Explain the importance of geologic time.

Our Solar SystemOur Solar System

Our Solar System evolved about 4.6 billion years ago from a cloud of dust and gas that rotated in space and eventually coalesced into the Sun, the planets and their moons under the pull of gravity. Yet today, all of the planets are different. Lets compare Venus, Mars and Earth.

Fig. 1-1, p.3

VenusVenus Is it hospitable? It most resembles Earth in size, density

and distance from the Sun, but atmosphere is rich in carbon dioxide and caustic sulfuric clouds fill the sky. Lead would melt at the surface…why so different then Earth?

MarsMarsEvidence of water. Its surface has similar features as Earth (water features such as extinct canyons, stream channels, lake beds). At one time this planet may have had flowing water; but today, it is frigid and dry with ice caps of frozen carbon dioxide.

Fig. 1-2, p.3

If these planets formed at the same time, why are they so different today? The original atmospheres of Earth, Venus and Mars evolved into swirling mixtures of carbon dioxide and carbon monoxide, water, ammonia, methane and other gases. Consider how H2O and CO2 exist on Earth.

• Venus: closer to the Sun, water never condensed, CO2 remained in the atmosphere (no seas to dissolve in). These greenhouse gases (H20, CO2) would have what effect?

• Earth cool enough for water vapor to condense, form oceans and dissolve CO2 from the atmosphere…so large quantities of greenhouse gases removed from the atmosphere and it cooled at a temperature favorable for liquid water and life. Our initial atmosphere replaced by an atmosphere rich in nitrogen and oxygen. Where did the oxygen come from?

* Mars a little farther from the Sun than Earth, less solar radiation. Initially rain fell, rivers flowed, and lakes/oceans formed (possibly life formed). But distance from Sun lowered greenhouse gases in atmosphere. Temperatures dropped (commonly below freezing to as low as -140 degrees C or -220 degrees F).

The Earth’s four spheresThe Earth’s four spheres

• Planetary changes are driven by complex interactions among the “spheres”…

• On Earth, what are they?

• Which one is largest? (see page 5).

1.2 The Earth’s four spheres1.2 The Earth’s four spheres

• Geosphere - the solid earth– Planets accreted from dust

into planetesimals– Planetesimals clumped

together to form planets– Colliding pieces (and

radioactivity) created heat, warming the young Earth to melting and differentiation into layers

– This ended (or Earth started) about 4.6 billion years ago

Fig. 1-4, p.6

The Earth’s Layers: Core, Mantle and CrustThe Earth’s Layers: Core, Mantle and Crust

• Metallic core: Fe and Ni, temp hot as Sun’s surface (6000 degrees C), inner core is solid, outer core is liquid.

• Less-dense rocky mantle: Changes with depth, some parts solid, others weak and plastic-like, flowing slowly.

• Least-dense crust: crustal material varies widely.

Granitic Rock of Baffin Island, CanadaGranitic Rock of Baffin Island, Canada(common rock of the continental crust formed from magma)(common rock of the continental crust formed from magma)

Fig. 1-5a, p.6

Sandstone and Limestone of the desert in Utah, USASandstone and Limestone of the desert in Utah, USA(how do these types of rock form?)(how do these types of rock form?)

Fig. 1-5b, p.6

• Lithosphere – the crust and upper part of mantle – Average 100km thick – Broken up into tectonic plates– Plates float atop the weaker material – 7 major (and several minor) plates are in

constant motion

The Earth’s InteriorThe Earth’s Interior• A slice through the Earth. According to Plate Tectonics Theory, the lithosphere is broken into segments called tectonic plates. They move on the asthenosphere at about the rate your fingernail grows. This movement accounts for earthquakes, volcanoes, other phenomena.

Fig. 1-6, p.7

Hydrosphere

All of Earth’s water

• Oceans not only contain 97.5% of Earth’s water, but cover 71% of the Earth’s surface.

• Glaciers cover 10% of the Earth’s surface and contain about 1.8% of its water.

• Only 0.01% is water at Earth’s surface (streams, lakes), 0.63% is underground and 0.001% is in the atmosphere

Fig. 1-7, p.7

• Atmosphere

• Mixture of gases, mostly nitrogen and oxygen.

• Held by what force?

• Mostly concentrated (99%) in the first 30 km above Earth.

• Supports life, acts as a filter (shield) and blanket. Transport heat around the globe.

Fig. 1-8, p.8

BiosphereBiosphere

• Zone inhabited by life.

• Includes the uppermost geosphere, hydrosphere and lower atmosphere.

• Plants and animals not only depend on the Earth’s environment, but alter and form the environment they live in.

Earth SystemsEarth Systems• System: assemblage or combination of interacting

components that form a complex whole. • Systems are driven by flow of energy and matter. Large

systems are composed of many smaller ones…the human body for example…and human’s interact in ecosystems, which interact with other Earth systems!

• Earth’s major systems are its spheres, subdivided into many interacting smaller ones. Discuss a volcanic eruption?

• What are Earth’s systems powered by?? • Several energy and material cycles are important in our

study of Earth’s systems…what is one of these? All spheres continuously exchange matter and energy. Earth’s materials and processes are part of one integrated system…

• The Carbon Cycle: All of Earth’s cycles and spheres are interconnected. For example, the formation and decomposition of limestone is part of the rock cycle because limestone is a rock. The same process is also part of the carbon cycle because limestone is composed partly of carbon.

Fig. 1-9, p.10

• Earth’s cycles and spheres are interconnected.

Fig. 1-10, p.11

Time and Earth ScienceTime and Earth Science

• James Hutton, 1700s. Regarded by many as the “Father of Geology”. Observed how sandstone formed, deduced the Earth must be very old.

• He formulated “uniformitarianism” (gradualism): geologic change occurs over long periods of time, by a sequence of almost imperceptible events (erosion, plate motions).

• “The present is the key to the past” (explain geologic events of the past by observing changes today).

• Not all change is gradual: “Catastrophism” occurs, this idea was put forth by geologist William Whewell (floods, earthquakes).

• Hutton observed that a sandstone outcrop, like this one in Utah, is composed of tiny round sand grains cemented together.

Fig. 1-11, p.12

Today we know from age dating rocks and other methods that the Earth is about 4.6 billion years old.

Fig. 1-12, p.13

-Most geologic change is gradual. Movement of tectonic plates is slow, yet accounts for mountains, volcanic eruptions, earthquakes and other geologic phenomena.-Catastrophic events have occurred throughout the 4.6 billion years of Earth’s history. 50,000 years ago, a meteorite crashed into the Arizona desert, creating meteor crater. Larger impacts may have caused mass extinctions (possibly killing the dinosaurs off 65 million years ago).

Fig. 1-13, p.14

1.5 Threshold and feedback 1.5 Threshold and feedback effectseffects

• Threshold effect – slow or no initial change to environmental change– When threshold point is passed, change becomes rapid

(for example, melting of glaciers).

• Feedback mechanism

– one change affects another system component, amplifying original effect…can be positive or negative.

• Today there are approx. 6.5 billion people on Earth.

• 40% of land area is developed.

• Species extinction rate is high.

• CO2 is at a high level (Earth’s temp raised .6 degree C since Industrial revolution).

• Do we have enough resources?

• Will our growth trigger climate changes? …

Fig. 1-14, p.15

Fig. 1-16, p.18

• Current trends– Population is

increasing, but slower (7-14 billion estimated when stable)

– India/China becoming richer – richer people consume more resources

– Population and consumption continue to rise with serious environmental consequence (see Table 1.1)

• How many people can Earth support?– Calculations of carrying capacity vary considerably– Increasing amounts of food can be produced– People can migrate from areas of famine or poverty to

less crowded or wealthier areas

Carrying CapacityCarrying Capacity

– BUT Earth’s resources are finite, so solutions are temporary

Carrying CapacityCarrying Capacity• Example of Rapa Nui (Easter Island)

– Isolated Pacific island with poor soil and little water– Settled by 25-50 Polynesians in 5th century

• Survived easily on chickens and yams, plenty of free time

• Developed elaborate competition between clans with moai (statues)

– Civilization peaked at 1550, with population of ~7000

• Example of Rapa Nui (Easter Island)– Reached by a Dutch ship in 1722

• Found about 2,000 people living in caves• Primitive society, constant warfare

– Rapa Nui’s carrying capacity had been drastically lowered by society’s actions:

• Transportation of moai had required cutting down trees

• Erosion of soil made yams scarce• Lack of canoes made fishing difficult and escape

impossible

Carrying CapacityCarrying Capacity

The Scientific Method (see page 15)The Scientific Method (see page 15)• Observation, Hypothesis, Theory and Law.• Observation: starting point of science. Collect facts.• Hypothesis: tentative explanation built on strong

supporting evidence. Tested by comparison, additional observations and experiments.

• Theory: If hypothesis explains new observations and is not substantively contradicted, can become a theory. Should be supported and explain many observations without major inconsistencies (theory of plate tectonics).

• Law: statement of how events always occur under given conditions. Considered factual and correct (law of gravity). Very few laws.

Fig. 1-15, p.16