Oceanography An Invitation to Marine Science, 8th Edition Tom Garrison Chapter 1: The Origin of the Ocean

OceanographyOceanographyAn Invitation to Marine Science, 8th EditionAn Invitation to Marine Science, 8th Edition

Tom GarrisonTom Garrison

Chapter 1:The Origin of

the Ocean

Chapter 1Study Plan

• Earth is an Ocean World• Marine Scientists Use the Logic of Science to

Study the Ocean• Stars and Seas• Earth, Ocean, and Atmosphere Accumulated

in Layers Sorted by Density• Life Probably Originated in the Ocean• What Will Be the Future of Earth?• Are There Other Ocean Worlds?

Chapter 1Six Main Concepts

• Science is a systematic process of asking questions about the observable world by gathering and then studying information. Science interprets raw information by constructing a general explanation with which the information is compatible. Explanations (theories) may change as our knowledge and powers of observation change; thus, all scientific understanding is tentative.

• The universe’s observable mass consists mostly of hydrogen atoms. Clearly, Earth and its inhabitants are not mostly made of hydrogen gas. The heavy elements we see around us were constructed in stars. Our solar system is the result of the accumulation of elements formed in stars and distributed into space by cataclysmic events at the end of their lives.

• Earth is density stratified; that is, as Earth formed, gravity pulled the heaviest materials (iron, nickel) to its center as lighter minerals rose to the surface. Earth’s first solid surface formed about 4.6 billion years ago.

• Although most of Earth’s water was present in the solar nebula during the accretion phase, a barrage of icy comets or asteroids from the outer reaches of the solar system colliding with Earth may also have contributed a portion of the ocean-to-be. The ocean is probably 4 billion years old.

• Life probably originated in the ocean shortly after it formed.• Water, even liquid water, appears to be present in a few other places in our

solar system.

Earth Is an Ocean World

Although the components of Earth are not rare in the universe, the unique combination of circumstances makes Earth extraordinary.

• Atoms and water molecules

• Planet size and characteristics

• Tranquil neighborhood• Earth’s orbit and

distance from sun


The relative amount of water in various locations on or near Earth’s surface. More than 97% of the water lies in the ocean.


Earth’s most prominent features. The average depth of the ocean is 4½ times greater than average land elevation.

Marine Science (or oceanography) integrates many different types of science:

• Marine geologists study Earth’s crust and composition.

• Physical oceanographers study of waves, currents, and climate prediction.

• Chemical oceanographers study the ocean’s dissolved gases and solids in the ocean.

• Climate specialists investigate the ocean’s role in Earth’s changing climate.

• Marine biologists study the nature and distribution of marine organisms.

• Marine engineers design and construct structures used in or on the ocean.

Marine Scientists Use the Logic of Science to Study the Ocean


Scientists and technicians aboard the R/V Oceanus launch a rosette - a ring of bottles to collect samples of water from various depths.

• Science is a systematic process of asking questions about the observable world by gathering and studying information (data).

• Science interprets raw information by constructing a general explanation with which the information is compatible.

• Scientists start with a question based upon something observed or measured.

• Working hypothesis – tentative explanation for the observation or measurement that can be tested and verified by further observations and controlled experiments.


• An experiment is a test that simplifies observation in nature or in the laboratory by manipulating or controlling the conditions under which the observations are made.

• Theory – a hypothesis consistently supported by observation or experiment.

• Laws – larger constructs that summarize experimental observations.

• A law summarizes observations while a theory provides an explanation for the observations.


What methods do marine scientists use to obtain and interpret data?

Scientific methods are not a simple set of steps followed by every researcher to answer every question. However, some questions can be answered by using the following method:

Ask a question

Form a working hypothesis

Observe or experiment

Form theories and laws


An outline of the scientific method, a systematic process of asking questions about the observable world and then testing the answers to those questions.


Stars Form Seas

• To understand the ocean, we need to understand how it formed and evolved through time.

• Scientists believe the origin of the ocean is linked to Earth’s origin.

• The origin of Earth is linked to that of the solar system and galaxies.

• The origin of the solar system and galaxies are linked the the beginnings of the universe and the big bang.

From the Big Bang to Stars

• The universe apparently had a beginning called the big bang that occurred ~13.7 billion years ago.

• All of the mass and energy of the universe was concentrated at a geometric point at the beginning of space and time, the moment when the expansion of the universe began.

• We don’t know what initiated the expansion, but it continues today and will probably continue for billions of years, perhaps forever.

• About a billion years after the big bang, the cooling matter began to congeal into the first galaxies and stars.

Stars and Planets are Contained within Galaxies

Our Milky Way Galaxy is estimated to be one of 100 billion galaxies in our universe and each may contain 100 billion stars. We’re inside and dust obscures our view, but this painting is a good guess about what our galaxy looks like, based on many different types of observations. Our solar system is a little more than half-way out from the center in one of the blue spiral arms.

What do stars have to do with the ocean?• Most of the substance of Earth, its ocean, and all

living things, were formed by stars.• Every chemical element heavier than hydrogen was

manufactured and released into space by stars.• The planet and even ourselves are made of this

stardust. Our bones and brains are composed of ancient atoms constructed by stellar fusion that occurred long before the solar system existed.

• Our sun, like all normal stars, is powered by nuclear fusion which creates heavier elements as well as light and heat.

Stars Make Heavy Elements from Lighter Ones

• Very large stars are much hotter and are able to create heavier atoms up to iron.

• When these stars run out of their nuclear fuel they can collapse in on themselves.

• When the infalling material can no longer be compressed, the energy is converted to a cataclysmic expansion called a supernova.

• This shock wave can cause the condensing mass of a solar nebula to spin and enrich the nebula with heavier elements.

Stars Make Heavy Elements from Lighter Ones

The origin of a solar system in the spiral arm of a galaxy. Our sun and its family of planets were formed in this way about 5 billion years ago.

Solar Systems Form by Accretion

Solar Systems Form by Accretion

Planet-building in progress. An artist imagines our solar system in its infancy. The sun has recently begun to shine, and planets are forming in the surrounding dusty disk. Accretion of planets occurs when small particles clump into large masses.

Earth Accumulated in Layers Sorted by Density

How did Earth become density stratified?• Young Earth was probably

homogeneous• Heat and gravitational pressure caused

Earth to partially melt• Gravity then pulled the iron present

into the center of Earth• This heated Earth further and lighter

minerals migrated to Earth’s surface and formed the crust

(TOP) The planet grew by the aggregation of particles. Meteors and asteroids bombarded the surface, heating the new planet and adding to its growing mass. At the time, Earth was composed of a homogeneous mixture of materials.

(MIDDLE) Earth lost volume because of gravitational compression. High temperatures in the interior turned the inner Earth into a semisolid mass; dense iron (red drops) fell toward the center to form the core, while less dense silicates move outward. Friction generated by this movement heated Earth even more.

(BOTTOM) The result of density stratification is evident in the formation of an inner and outer core, a mantle, and the crust.

Earth Accumulated in Layers Sorted by Density

Stepped Art

Iron

Lightermatter andsilicates

Figure 1-11 p15

Moon Formation

• A planetary body somewhat larger than Mars smashed into the young Earth about 4.4 billion years ago.

• The rocky mantle of the impactor was ejected to form a ring of debris around Earth, and its metallic core fell into Earth’s core and joined with it.

• Within a thousand years of the giant impact, our moon was forming.

• The Sun stripped away Earth’s first atmosphere

• Gases, including water vapor, released by the process of out-gassing, replaced the first atmosphere.

• Water vapor in the atmosphere condensed into clouds.

• Eventually, the surface cooled enough for water to collect in basins.

Sources of the Ocean

How did water and water vapor form on early Earth?

Volcanic gases emitted by fissures add water vapor, carbon dioxide, nitrogen, and other gases to the atmosphere. Comets may have delivered some of Earth’s surface water. Intense bombardment of the early Earth by large bodies – comets and asteroids – probably lasted until about 3.8 billion years ago.

Sources of the Ocean

Life Probably Originated in the Ocean

• The early steps in the evolution of living organisms from simple organic building blocks, a process known as biosynthesis, are still speculative.

• The first living molecules might have arisen at great depths at mineral-rich seeps on the ocean floor.

• Life on Earth almost certainly evolved in the oceans; the cells of all life-forms are still bathed in salty fluids.

What Will Be the Future of Earth?

• Our Sun will run out of fuel and begin to die in about 5 billion years.• It will enter a red giant phase and will engulf the inner planets.• At that time, Earth will probably be recycled into component atoms.

Are There Other Ocean Worlds?

• Our Solar System’s Outer Moons– Europa: The gravitational pull of Jupiter twists

Europa, cracking the ice crust and warming the interior. Evidence suggests the ice crust is lubricated by slush or water. It may also be salty - salinity has been detected by Galileo’s magnetometers.

– Ganymede: Jupiter’s largest satellite shows structures strikingly similar to those on Europa. Again, magnetometer data suggested a salty ocean beneath a moving, icy crust.

– Enceladus: Cassini’s cameras detected fountains of ice crystals shooting from gashes on Saturn’s small moon’s surface.

Are There Other Ocean Worlds?

• Mars– Early in its history, Mars may have had a thick

atmosphere of carbon-dioxide and an ocean.– Over the eons, rocks on the Martian surface

absorbed the carbon dioxide and the atmosphere grew thin and cold and the ocean disappeared

• Titan – Saturn’s largest moon

may have an ocean of hydrocarbons.• Extrasolar Planets

Chapter 1 in Perspective

In this chapter you learned that Earth is a water planet, possibly one of few in the galaxy. An ocean covering 71% of its surface has greatly influenced its rocky crust and atmosphere.

We study our planet using the scientific method, a systematic process of asking and answering questions about the natural world. Marine science applies the scientific method to the ocean and the living organisms dependent on the ocean.

Most of the atoms that make up Earth and its inhabitants were formed within stars. Stars form in the dusty spiral arms of galaxies and spend their lives changing hydrogen and helium to heavier elements. The sun and the planets, including Earth, probably condensed from a cloud of dust and gas enriched by the recycled remnants of exploded stars. Earth formed by the accretion of cold particles about 4.6 billion years ago.

Heat from infalling debris and radioactive decay partially melted the planet, and density stratification occurred as heavy materials sank to its center and lighter materials migrated toward the surface.

The ocean formed later, as water vapor trapped in Earth’s outer layers escaped to the surface through volcanic activity during the planet’s youth. Life originated in the ocean very soon after its formation. We know of no other planet with a similar ocean, but water is abundant in interstellar clouds and other water planets are not impossible to imagine.

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Oceanography An Invitation to Marine Science, 8th Edition Tom Garrison Chapter 1: The Origin of the Ocean