Introduction to Oceanography Chapter 1: The Origin of the Ocean Insert: Textbook cover photo

Chapter 1 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 1: Six 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.

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

Marine Scientists Use the Logic of Science to Study the Ocean 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.

Marine Scientists Use the Logic of Science to Study the Ocean 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

Marine Scientists Use the Logic of Science to Study the Ocean 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.

Stars Make Heavy Elements from Lighter Ones 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.

Solar Systems Form by Accretion 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 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

Earth Accumulated in Layers Sorted by Density (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.

Lighter matter and silicates Iron Stepped Art Figure 1.11 Representation of the formation of Earth. Stepped Art 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.

Sources of the Ocean How did water and water vapor form on early Earth? 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 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.

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