Chapter 1: INTRODUCTION TO PLANET "EARTH"

oceans: the entire body of saltwater that covers 70.8% of Earth’s surface

  • largest and most prominent feature on Earth

  • volume of oceans is immense: 97.2% of surface water

  • interconnected global or world ocean

  • contains the greatest number of living things on the planet

1.1 How are Earth’s Oceans Unique?

  • Earth is only planet that has liquid water on its surface

How many oceans exist on earth?

  • Four principal oceans

    • Pacific: largest, deepest

      • 13,000 feet

    • Atlantic: second largest

    • Indian: mainly the southern hemisphere

    • Arctic: smallest, shalowest, northern hemisphere, icy

  • Southern/Antarctic: surrounds Antarctica in the southern region, connects pacific, atlantic and indian

Comparison of land and depth

  • average depth of ocean 3729 m

  • average elevation of land 840 m

  • deepest ocean Mariana Trench 11,022 m

  • Highest mountain Mt. Everest 8850 m

1.2 How was Early exploration of the Oceans Achieved?

  • Pacific Islanders traveled Pacific widely for food 40,000 years ago

    • small islands widely separated

    • micronesia, melanesia, polynesia

  • Pacific navigators

    • the people of pacific islands required extensive travel in open boats and exceptional navigation skills

    • difficult because islands are widely scattered

Pacific People

  • no written records exist of Pacific human history before 16th century

  • archeological evidence suggests island occupation by people from New Guinea as early as 4000-5000 B.C.

  • Thor Heyerdahl sailed on a balsa raft - the KON TIKI to demonstrate migration of south americans to pacific ocean

European Navigators

  • Phoenicians: lived at eastern end of Mediterranean sea around Africa and sailed as far north as British Isles

    • Phytheas greek astronomer-geographer reached Iceland 325 BC

    • Herodotus map med. areas 450 BC

Romans

  • strabo land rises and sinks

  • ptolemy map of world at that time 150 AD

The Middle Ages

  • Vikings explored North Atlantic Ocean

    • iceland and greenland 9th and 10th centuries Ad

    • Leif Eriksson Vinland 995 AD

    • Greenland, Vinland settlements abandoned by 1450 AD

Chinese

  • Pacific and Indian Oceans

Age of Discovery

  • 30 year period from 1492 to 1522

    • portugal trade routes around africa

    • europeans explore north and south america

      • columbus, cabot

    • Magellan and del Cano circumnavigate world

  • British Isles dominant naval power from 1588 to early 1900s

    • spanish armada 1588

  • New technologies at those times

    • magnetic compass, china, 13th century

    • three-masted ships long distance

    • maps with latitude/longitude 1569

Beginnings of Ocean Science

  • Captain James Cook (1728-1779)

    • ships HMS Endeavour, Resolution, Adventure

    • mapped many islands in pacific

    • systematically measured ocean characteristics

    • marine chronograph (longitude)

  • John Ross, James Ross

    • Distribution of life in oceans

    • arctic and antarctic

    • amount of life in ocean lessens with increasing depth

  • Edward Forbes

    • hardly any life in deep oceans

  • Fridtjof Nansen

    • Fram

    • Arctic Ocean

    • V. Walfrid Ekman, Ekman spiral, Ekman Transport

Early American contributions

  • Benjamin Franklin

    • postmaster general

    • map of gulf stream

  • Matthew Maury

    • father of oceanography

      • first textbook

  • Alexander Agassiz

    • U.S. oceanographic research

HMS Challenger 1872-1876

  • Birth of oceanography

  • seawater chemistry, depth, temperature, life, sediments

  • 4714 new species

  • deepest depth

  • analyses of seawater

  • classification of deep sea sediments

20th Century new technologies

  • Meteor, 1925, German, echo sounding

  • increased insturmentation

    • gravity

    • magnetic field

    • seismic structure of sea floor

Deeper sampling of sea floor

  • 1968 ongoing, deep sea drilling project

    • different project names

    • currently international sponsorship

  • drill through sediments on ocean floor

Modern fields of research

  • marine geology

  • marine geophysics

  • ocean geochemistry

  • ocean currents

  • climate change

  • marine life

Plate Tectonics from DSDP

  • geophysics applied to ocean floor

  • Hess develops sea floor spreading concept

Submersibles and ROVs

  • deep-diving small submarines

    • first-hand look at sea floor

    • hot vents, unique ecosystem

  • Remotely operated vehicles (ROV)

    • instruments to collect information

    • not staffed

Dives to the deepest part of the Mariana Trench

  • Don Walsh, 1960 on the Trieste

  • James Cameron, 2012 on the Deep Sea Challenger

  • Victor Vescovo, 2019 on DSV limiting factor, 35,849 ft! Finds a Plastic Bag!

Satellites

  • instruments on satellites

  • global scale

    • measure characteristics on ocean surface

    • surface temperature

    • ice cover

  • water color

    • changes in sea level

Underwater human habitats

  • continental shelf

  • mainly in 1960s

  • three small underwater habitats today (Key Largo, FL)

    • mainly for research

1.5 how were earth and the solar system formed?

  • the “Big Band” 13.7 Ga is accepted as the start of the Universe. The term Big Band was first used by Sir Fred Hoyle

  • First 200 million years “Dark Ages”

    • gasses (H, He) start to condense and stars begin to form

    • approx. 500 billion Galaxies in the Universe

    • Our galaxy (milky way) has approx. 400 billion stars and 10s of millions have planets

Universe

  • milky way galaxy

    • Solar System: the sun and the celestial bodies, asteroids, planets, and comets that orbit around it

  • light year for distance

  • galaxies moving apart (red shift)

  • nebula: a cloud

Stellar Evolution

  • All stars initially contract, H → He (Fusion) and light is emitted

  • subsequent contraction results in nucleosynthesis, leading to the formation of the heavier elements

  • stars form an iron core and contracts and explodes, the gas cloud derived from an exploding star is called a supernova. a neutron star forms a remnant of a supernova event

  • nebular is an interstellar gas cloud

  • our solar system formed from the gas cloud derived from an exploding star approx. 5 billion years ago

Big Band

  • elementary particles

  • H and He

  • Stars from H → He

  • He → C and so on

  • Supernova explosions eject heavier elements

Nebular Hypothesis

  • all bodies in the solar system formed from an enormous cloud composed mostly of hydrogen and helium, with a small percentage of heavy elements

  • rotating cloud of dust and gases

  • supernova earlier

  • center sun

  • outskirts

  • planets

Early evolution of Earth

  • origin of planet earth

    • nebular hypothesis

      • assumes a flat, disk shape with the protosun (pre-sun) at the center

      • inner planets begin to form from metallic and rocky substances

      • larger outer planets began forming from fragments of ices (H2O, CO2, and others)

      • rotating cloud called the solar nebula

      • composed of hydrogen and helium

      • nebula began to contract 5 million years ago

    • most researchers believe that Earth and the other planets formed at essentially the same time

  • Professor Kuiper

    • talked about early nebular hypothesis in his work

  • formation of earth’s layered structure

    • metals sank to the center

    • molten rock rose to produce a primitive crust

    • chemical segregation established the three basic divisions of Earth’s interior

    • Primitive atmosphere evolved from gases in earth’s interior

A view of Earth

  • Earth is a planet that is small and self-contained

  • Earth’s four spheres

    • Hydrosphere

    • Atmosphere

    • Biosphere

    • Solid Earth

Proto-planet to Earth

  • Layered Earth

  • Densest core

    • Fe and Ni

  • Less dense material in mantle

  • still less material in crust

  • least dense material in atmosphere and ocean

Earth’s Internal Structure

  • Layers defined by composition

    • crust: The outermost layer of the Earth, composed primarily of silicate rocks, which can be divided into continental and oceanic crust.

    • mantle: the zone between the core and the crust of the earth; rich in ferromagnesian minerals

    • core: the deep, central layer of Earth, composed primarily of iron and nickel; subdivided into liquid outer core and solid inner core

  • Layers defined by physical properties

    • lithosphere: earth’s cool, rigid, outermost layer; brittle and includes the crust; divided into tectonic plates that move and interact, leading to geological activities such as earthquakes and volcanic eruptions.

    • asthenosphere: plastic; it will flow when a gradual force is applied to it; it lies beneath the lithosphere and is composed of partially molten rock, allowing tectonic plates to glide over it, thereby facilitating their movement.

    • Mesosphere: the layer of Earth’s mantle located beneath the asthenosphere; it is characterized by its solid state and increased temperatures, which can reach up to 4,000 degrees Celsius, contributing to the dynamics of mantle convection and further influencing tectonic plate behavior.

    • Inner and outer core: the innermost layers of the Earth; the inner core is solid, primarily composed of iron and nickel, and has temperatures that can exceed 5,000 degrees Celsius, while the outer core is liquid and plays a crucial role in generating the Earth’s magnetic field through the movement of molten metals.

Rocks

  • rocks made of minerals

  • igneous rocks

    • molten rock material

    • basalt - oceanic crust

    • granite - continental crust

  • Sedimentary rocks

    • pre-existin rocks

    • weathered fragments

    • dissovled ions

    • lithified

    • sandstone

    • limestone

  • Metamorphic rocks

    • transformed pre-existing rocks

    • higher pressure

    • higher temperature

    • not molten

    • roots of mountains

Minerals

  • Most Common mineral in crust and mantle

    • silicates

      • silicate tetrahedron

      • four oxygen

      • one silicon

      • SiO4

  • Common minerals on the ocean floor

    • Silica (SiO2): weathering of continents and shells of organisms

    • Carbonate (CaCO3): shells of organisms and precipitates from ocean water

    • clays: weathering of continents

    • Salts: evaporation of saltwater

  • Formation of minerals

    • minerals form by the sharing (covalent) and/or exchange (ionic) of electrons between atoms of elements.

    • Occurs in nature because the tendency in nature is to achieve a stable state by filling the outer shell of electrons

    • Covalent bond: SiO2

    • Ionic bond: NaCl

  • Isotopes

    • atoms of an element that contain different numbers of neutrons (1H, 2H, 3H)

    • 16O, 17O, 18O

    • 12C, 13C

    • Some isotopic are stable (1H, 2H) and others are unstable (3H)

Fractionation

  • the redistribution of the stable isotopes of an element

  • we will see there are a variety of of ocean processes that result in fractionation

    • evaporation, condensation

    • photosynthesis

1.6 How were Earth’s atmosphere and oceans formed?

Origin of Earth’s Atmosphere

  • outgassing: the release of gases from Earth's interior during volcanic activity, played a crucial role in creating the early atmosphere and contributing to the formation of oceans.

    • released by partial melting

Origin of Earth’s Oceans

  • H2O released by outgassing

  • condenses to form water

  • water evident in oldest rocks

    • about 4 billion years ago

  • oceans on other planets/mood

    • distance from sun

    • rotational period

    • natural greenhouse effect

Alternative hypothesis for formation of the oceans

  • Continuous delivery of water to earth by comet bombardment

    • lewis frank (1997)

  • Earliest atmosphere composition like modern volcanoes

    • dominantly CO2, H2O, N2, and others

  • modern atmosphere N2, O2, Ar

    • O2 from photosynthesis

  • some discussion based on stable isotope data that oxygen levels may have been higher during the early archean that previously thought (H. Ohmoto, Penn. St.)

Ocean Salinity

  • saltiness

  • rain/rivers deliver dissolved ions to oceans

  • volcanic gases deliver “ions” to ocean

  • dissolved ions precipitate to form minerals and shells

  • ocean salinity balance of input and output of ions

Mass balance and cycling

  • water in ocean from mantle

  • salts in ocean from rocks on land

  • salts in ocean from volcanoes

1.7 Did life begin in the Oceans?

Life

  • self-replicating

  • separate from environment (membrane)

  • responds to environment

  • carbon-based (on earth)

  • contains water

Importance of Oxygen to life

  • oxidize food to provide energy for cellular processes, enabling growth and survival of living organisms.

  • deconmposition

  • ozone stratosphere takes in ultraviolet radiation

    • UV dangerous for most living organisms

    • ocean readily absorbs UV

    • likely life developed in ocean

Stanley Miller’s Experiment

  • first organic substances H, C, and N

  • 22 year old graduate student chemist

    • CO2, CH4, NH3, H, and H2O

    • electricity

    • mixed they made prebiotic soup

    • amino acids and nucleotides

First organic molecules

  • life started in ocean with lighting?

  • life started at hot vents using geothermal energy?

  • life from outer space?

Problems

  • early atmosphere of the earth was oxidizing (carbon dioxide, water, nitrogen) and an oxidizing atmosphere is not conducive to organic sythesis

  • miller type experiments result in “racemic” mixtures of organic compounds

  • life as we know it is based on enantiopure compounds (L-amino acids and D-sugars) which are a necessary precondition to form the alpha-helix

Origin of Chirality in the Solar System

  • prebiotic synthesis on meteorite parent body

  • partial destruction of d-amino acides by CPL from neuron stars

  • Enhanced L-excess by solid-liquid phase interactions on the parent body

  • Meteorite impacts on early earth

Plants and Animals Evolve

  • Heterotrophs: very earliest forms of life

    • external food supply

    • fermenting bacteria

  • Autotrophs: manufacture their own food supply

    • anaerobic bacteria

    • chemosynthesis: able to derive energy from inorganic compounds at deep water hydrothermal vents using a process

Photosynthesis and Respiration

  • Photosynthetic organisms

    • sunlight energy

    • earliest may have used H2S

    • earliest cyanobacteria 3 billion years ago

  • oxygen released “polluted” early atmosphere

    • atmosphere no longer dominant

Multicellular life

  • prokaryotic cells

    • earliest

    • single celled

    • no nucleus

    • no internal membrane

  • Eukaryotic cells

    • earliest fossil evidence 1.4-1.6 billion years ago

    • multi-celled

    • nucleus

    • complex membranes

    • intracellular bodies

Problems interpreting the fossil record

  • microfossils interpreted as being of great antiquity have sometimes been shown to be either pseudofossils or contaminants

  • much of the biomarker evidence for early cyanobacteria and eukaryotic from australia has been recently retracted

evolution

  • organisms change through time

    • responsive to environment

    • change environment

  • major changes in life forms

  • extinction events

GREAT OXIDATION EVENT/ OXYGEN CRISIS

1.8 How old is Earth?

Radiometric Age Dating

  • extremely powerful tool for determining the age of rocks

  • radioactive elements change spontaneously

  • fixed rate of change

  • ratio of original to decayed product is proportional to time or age

  • half-life is time to change ½ original to product

    • half-life: the time required for one half of the atoms in a sample to decay to other atoms

Geologic Time Scale

  • lists the names of geologic time periods as well as important advances in the development of life-forms on Earth

    • time periods

    • ages of boundaries

    • major extinction episodes

    • oldest rocks about 4 billion years old