What makes Earth the “Blue Planet”?

= x 100  70.9% of Earth’s surface 361.8x10 6 km x10 6 km 2 Earth’s total surface area = 510x10 6 km 2 (= 4  R 2, where R = Earth’s radius = 6371 km and  = 3.14)  Ocean surface area Earth is called the “Blue Planet” because water covers >70% of Earth’s surface Ocean surface = x10 6 km 2 Earth’s sur face Land surface = x10 6 km  510 x km 2

The World Ocean Area (10 6 km 2 ) Mean Depth (km) Volume (10 6 km 3 ) Pacific Ocean Atlantic Ocean Indian Ocean

This view from above the North Pole shows the Arctic Sea at the center. When global warming melts the polar ice cap here, will that hurt the polar bear or help? Mother Polar Bear and Cubs Emerging from Den in this BBC Planet Earth Mother Polar Bear and Cubs Emerging from Den in this BBC Planet Earth video clip. Amazing images taken from the Arctic circle as a mother bear emerges from her winter long sleep with two new arrivals. With brilliant images of... 1 year ago 65,462 views

This is the view of the Earth from above the South Pole. Notice Antarctica at the center. The ocean surrounding it, the Southern Ocean, has very high biological pro- ductivity, thanks to the vigorous rotation-driven circulation called West Wind Drift. Little wonder the penguin forgot flying, making us wonder if the Penguin is really a bird!

Equator divides the Earth into two equal halves, with North Pole at the center of one half and South Pole at the center of the other.

... and water is blue becauseits absorption bands extend through the red part of the visible spectrum (red light absorbs 100 times... and water is blue because its absorption bands extend through the red part of the visible spectrum (red light absorbs 100 times Absorption coefficient (cm -1 ) 100 nm 1 μm 10 μm Wavelength more than blue light). Together with the five-times greater scattering of blue light over red light, his absorption spectrum of water contributes to the blue color of lake, river and ocean waters. Together with the five-times greater scattering of blue light over red light, this absorption spectrum of water contributes to the blue color of lake, river and ocean waters.

Water is a chemical compound, H 2 O, that … forms from the joining of one oxygen and two hydrogen atoms, i.e., 2H 2 + O 2  2H 2 O and survives between 0ºC and 100ºC temperatures. We should therefore find water at all the locations having adequate quantities of hydrogen and oxygen and 0ºC ― 100ºCtemperatures. We should therefore find water at all the locations having adequate quantities of hydrogen and oxygen and 0ºC ― 100ºC temperatures.HydrogenOxygen

Abundance relative to Si = 10 6 Atomic Number (Z) Click on this image to access NOVA History of the Universe Judging from chemistry, water should abound all over the universe. Hydrogen Helium OxygenCarbonNitrogenSiliconNeonMagnesiumIronSulphurAluminumCalciumNickelSodiumArgonChromiumPhosphorousManganeseChlorinePotassium H He OCNSiNeMgFeSAlCaNiNaArCrPMnClK Composition of the Universe

Mass of the star, relative to Sun Radius of planetary orbit, relative to Earth EarthVenus Mercury Mars JupiterSaturnUranusNeptune Habitable zone 20 Using the concept of black body radiation, we can compute if the planetary surface is hot enough for water to exist, because a black body emits away all the incident radiation that it receives, i.e., Total Incident Power (P incident ) = Total Outgoing Power (P emitted ) Now, P incident = (1–α)LπR² for a planetary disc of radius R, where L is incident radiation and α is albedo, the proportion of heat that is reflected away (i.e., α = 0 when the entire incident radiation is absorbed and α = 1 when the entire incident radiation is reflected away. As the heat emitted by the planet is over its entire surface, P emitted = 4σT4πR² where σ = 5.67x W/m 2 K 4 is the Stefan-Boltzmann cons-tant and T is the planetary surface temperature in Kelvin. For P incident = P emitted and α = 0, we then have L = 4σT 4. This yields L = 1260W/m 2 for T = 273K (0°C) to L = 4390W/m 2 for T = 373K (100°C). This region is called “habitable zone”.

This stunning picture of sunset at the North Pole was taken in August 2009

Evaporation 320,000 km 3 Evaporation 60,000 km 3 Ocean storage 1,370,000,000 km 3 Precipitation 285,000 km 3 Precipitation 95,000 km 3 Run-off: 35,000 km 3 NASA | Earth Science Week: NASA | Earth Science Week: Water, Water Everywhere! 6:32 A conceptual look at the hydro- logical cycle. Notice three aspects of it: 1.Evaporation exceeds precipitation over the oceans, but precipitation exceeds evaporation on land. 2.Currently, atmosphere transfers by precipitation all the water it receives by evaporation. 3.Run-off carries excess water as also rock materials from land to the oceans. Run-off also erodes rock materials from land and piles them as sediments on the continental margins

Two Questions 1.How and why does atmosphere return all the evaporated water back to the Earth? 2.Does run-off only take the land’s excess (i.e., P-E) water to the ocean or carries something additional?

As for the first question, troposphere’s temperature gradient forces the return of evaporated waters back to the Earth. Pressure Weather zone Altitude

Wilson Cycle ― which ensures the continuous reshaping of Earth’s surface geography, such that new ocean basins are created where we once had land and the new surface area thus created is balanced by an equal surface area in the mountain belts and deep sea trenches ― answers the second question.

Mount Annapoorna, 26,545 ft (8,091 m) This Himalayan peak, Mount Annapoorna, is made up of limestones with ~200 Ma old ammonite fossils, suggesting that an ocean once existed where we now have the world's tallest mountains!

Clearly, an ocean existed at this location ~250 Ma ago, when these limestones formed. ~250 Ma old Kaibab limestones form the floor of the Kaibab National Forest where the Grand Canyon National Park is located.

This animation of Alfred Wegner’s PANGEA, a supercontinent that existed ~250 Ma ago, shows how Atlantic and Indian oceans formed from PANGEA’s dispersal, a process that also created the Himalayas, Andes and Alps.

New ocean floor is created by spreading about the mid-ocean ridge, the site of incessant basalt volcanism

The new surface area created by sea-floor spread is compen- sated by loss of equal surface area at the Folded Mountain Belts (above) and Deep Sea Trenches (left)

As this map shows, the relative youth of ocean floor is a peculiarity of the world geological map

The older sea floor tends to be farther from the ridge axis Age of the sea floor (Ma BP)

This animation of Alfred Wegner’s PANGEA, a supercontinent that existed ~250 Ma ago, shows how Atlantic and Indian oceans formed from PANGEA’s dispersal, a process that also created the Himalayas, Andes and Alps.

The spreading seafloor records the geomagnetic polarity reversals that occur as the basaltic seafloor forms.

H O H 2H 2 + O 2  2H 2 O

2H 2 + O 2  2H 2 O H O H O H H H O H H O H

Water is a chemical compound that forms from the joining of one oxygen and two hydrogen two hydrogen atoms, i.e., atoms, i.e., 2H 2 + O 2  2H 2 O HydrogenOxygen

Bulleted cartoons Let us look at

Abundance relative to Si = 10 6 Atomic Number (Z) Hydrogen Helium OxygenCarbonNitrogenSiliconNeonMagnesiumIronSulphurAluminumCalciumNickelSodiumArgonChromiumPhosphorousManganeseChlorinePotassium Other elements H He OCNSiNeMgFeSAlCaNiNaArCrPMnClK Earth Earth Universe Universe Note that chemistry is not the reason why water should occur all over the occur all over the universe. universe.

O E C A 7 N ( % 8 0. ) L ( A N D % ) Ocean ridges (22.1%) Continental platforms (18.9%) Ocean basin floors (29.8%) Continental shelf and slope (11.4%) Island arcs, trenches, guyots etc. (3.7%) Continental rise (3.8%) Conti- nental mountains (10.3%)

Click on this image links to access the NOVA History of the Universe