The Origin of the Ocean

The Water Planet

AN OCEAN WORLD

• The ocean covers 71% of Earth’s surface • The ocean contains 97% of the water on Earth • The ocean is Earth’s most important feature • The named oceans and seas (Pacific and Atlantic, Mediterranean and Baltic) are named for our convenience • They are only temporary features of a single world ocean • Average ocean depth is about 4½ times greater than the average height of the continents above sea level

Earth is a Water Planet

• • • • • oceans occupy 71% of the earth's surface not distributed equally with respect to the equator ocean covers 61% of the northern hemisphere and 80% of the southern hemisphere presence of oceans is function of geological activity and planet's location in relation to sun – too far away -- water will be in a frozen state – too close -- water will evaporate Earth is in a perfect location to allow water to be in liquid state

• • • • •

Oceans

Today's oceans are traditionally divided into 4 large basins

–

North and South Pacific

– – –

North and South Atlantic Indian Arctic Oceans are really interconnected Connected to these 4 large basins are smaller, marginal seas, such as the Mediterranean, Gulf of Mexico, South China Sea, Red Sea, Caribbean, Baltic Sea, Bering Sea, etc. Each basin or marginal sea varies in its ability to support life due to both climatic differences and shapes and positions of present-day continents Ocean basins consist of the deep seafloor (13,000 20,000 ft; 4-6 km) and cover most of the earth's surface (30%); continents only cover 29%

Distribution of land and sea by latitude

Hypsographic Curve Elevation areas above And below sea-level

Bathymetric Chart of the Sea Floor

Physiographic Map of the Sea Floor

3-D Computer Generated Image of the East Pacific Rise

The Big Bang

• • • • Event that occurred approximately 13.7 BILLION years ago All the mass and energy concentrated at a point The universe began expanding and continues to expand After 1 million years matter began to cool enough to form atoms- Hydrogen- the building block of stars

Galaxies and Stars

• • • Galaxy- huge rotating aggregation of stars, dust, gas held together by gravity Earth, the sun and our solar system is part of the Milky Way Stars are massive spheres of incandescent gases (hydrogen and helium)

The Solar System

• • • • Our solar system is located away from the galaxy’s center Our sun and the planets originated from a solar nebula that had been enriched with heavy elements from nearby super novae Solar system is approximately 5 Billion years old Composition is 75% hydrogen, 23% helium and 2% other materials

Formation of a Protostar

Center contracts Center continues to heat up Protostar radiates more heat

Fusion begins in the stars core

Shockwaves radiate outward releasing material Material coalesces into planets, moons or comets Other material is ejected to the periphery

Our Solar System 4 inner planets (terrestrial) 4 outer planets (gaseous)

Solar nebula photographed by Hubble

• •

The Earth

Core

is composed of mixtures or alloys of iron (pressure is more than a million times that at the surface and temperature is estimated to be at 4000°C); has a solid inner core and a liquid outer core (earth's magnetic field may be produced by the motion of the liquid material in the iron-rich outer core) Layer outside the earth's core is the

mantle

; it is solid but very hot, near the melting point of rocks, so it flows almost like a liquid, though much slower; it is 70% of the earth's volume

The Earth

• Outermost layer is the (is thinner under the oceans than under the continents) –

Oceanic crust

compared to

crust

is made of ; it is extremely thin basalt high in iron and magnesium) and has a higher density

continental crust

(low in silica and , which is made of granite silicate with quartz and feldspar) and has a lower density (high content of aluminum and magnesium – Thus, continents lie above sea level and oceanic crust lies below sea level because of density differences

• • • •

Formation of the Oceans: Prevailing Theory

The major trapped volatile was water (H2O). Others included nitrogen (N2), the most abundant gas in the atmosphere, carbon dioxide (CO2), and hydrochloric acid (HCl), which was the source of the chloride in sea salt (mostly NaCl).

The volatiles were probably released early in the Earth's history, when it melted and segregated into the core, mantle, and crust. This segregation occurred because of differences in density, the crust being the "lightest" material.

Volcanoes have released additional volatiles throughout the Earth's history, but probably more during the early years when the Earth was hotter.

Probably, the oceans formed as soon as the Earth cooled enough for water to become liquid, about 4 billion years ago. The oldest rocks on the earth's surface today are 3.8 billion years old.

Outgassing

Oceans are byproducts of heating and differentiation: as earth warmed and partially melted, water locked in the minerals as hydrogen and oxygen was released and carried to the surface by volcanic venting activity

Origin of Atmosphere

• Atmosphere evolved in 4 steps: – primordial gases, later lost from sun's radiation – exhalations from the molten surface (volcanic venting); bombardment from icy comets – steady additions of carbon dioxide, water vapor, carbon monoxide, nitrogen, hydrogen, hydrogen chloride, ammonia, and methane from volcanic activity – addition of oxygen by plant/bacterial life

The Hydrologic Cycle

• • • • Water occurs as a solid, liquid and gas Amount of water is fixed The places where water resides are called

Reservoirs

Water constantly moves from one reservoir to another

Comparison of the amount of water supply held in each of the major reservoirs If the total earth’s water supply was a 55 gallon drum

The Origin of Sea Salts

• • • • The sea became salty because of chemicals leached from the rocks of the crust, plus some volatile chemicals (hydrochloric acid and hydrogen sulfide) released from the Earth's interior and by volcanoes. Probably, the ocean was salty as soon as it formed. More salts have accumulated gradually, as more of the rocks of the crust were broken down by water (weathered).

The composition of the sea salt has been about the same for about 1 billion years. That is because a balance exists between input of salts (mainly by rivers) and output (mainly by sediments).

The early ocean, 3.8 billion years ago, was probably similar in composition to today, except for changes caused by living things. The most important of these is the production of oxygen by plants.

The Origin of Life

Europa (Moon of Jupiter)- Icy Crust

Other Ocean Worlds

Drainage Systems on Mars

Ice Sand