Origin of the Atmosphere and Ocean

1. Origin of the atmosphere and ocean • First read this verse: يقول الله تعالى: ”الذين يذكرون الله قياما وقعودا وعلى جنوبهم ويتفكرون فى خلق السموات والأرض ربنا ما خلقت هذا باطلا سبحانك فقنا عذاب النار“ سورة آل عمران, آيه 191

2. Origin of the atmosphere and ocean • Earth’s surface solidifies gradually in a period ranging from 50 to 100 millions yrs. This solidification of the Earth’s crust that occurred about 4.5 billion yrs ago, marks the beginning of the Geologic History on Earth. At this stage, the Earth lost its original gas envelope and its crust became cool. • The volcanic activity and meteor bombardment were still intense until 3.9 billion yrs.

3. Formation of the atmosphere • Volcanic activities released much quantities of water vapor (H2O), carbon dioxide (CO2), chlorine gas (Cl2), hydrogen and Nitrogen (N2). Also, methane (CH4) and ammonia (NH3) occurred. • As Earth cooled, the water vapor in the atmosphere condensed and fell to the Earth’s surface to form the ocean water at about 4 billion yrs ago.

4. Origin of ocean water • Two assumptions explaining the ocean water sources: • 1- From the Mantle where the water vapor is brought out to the atmosphere via the volcanic activities, then condensed to fall on the earth’s surface forming the ocean water that is in permanent existence since its formation at 4 billion yrs ago (fossilized algae, marine environment). What is the evidence for this assumption? Mantle volume=1027cm3, density=4.5 g/cm3 Mantle mass=4.5*1027 g Ocean water mass=1.4*1024 g So, mantle must have lost 0.031% of its mass Meteorites contain 0.5% water which is about 16 times bigger than the loss required from the mantle to account for the present ocean water.

5. يقول الله تعالى: ”والأرض بعد ذلك دحاها . اخرج منها مآءها ومرعاها . والجبال ارساها . متاعا لكم ولأنعامكم“ سورة النازعات, آيه (30-33)

6. 2- From the space (Louis Frank, space scientist): Ocean water came to earth as comet-like ball of ice about 9 m in diameter entering to the earth’s atmosphere via dark holes (48 km wide) by rate of about 20 per minute. So, earth would receive 0.0025 mm of water per yr. In four billion yrs, the ocean would fill to the present volume. Since that time ocean water started to recycle to account for the eroded sedimentary succession on earth, with new little addition (1%) from the mantle by the volcanic activities. Thurman balance supports this assumption!

7. Ocean salinity • Salinity is a measure of number of ions (e.g. Cl-, Na+, Ca++, K+, Mg++, SO4--) in the ocean water. • Present day ocean salinity averages 35 ‰. • Salinity measures the number of ions (Cl-, Na+, Ca++, K+, Mg++, SO4--) in the ocean water. These ions are referred to as the major or conservative ions. They constitute over 99.8 % of the mass of solutes dissolved in seawater. • Salinity defined as the total number of grams of dissolved salt ions present in 1 kg of seawater. Mathematically expressed as parts per thousand (‰).

8. The most important component (ion) of salinity is the chlorine ion (Cl-), which is produced by volcanic activities. At 4.5 billion years, ocean water formed from the condensation of the atmosphere volatiles and water water vapor (H2O). Since that time, salinity developed in the ocean due to adding more substances from the rainfalls and earth's crust and is relatively constant with no indication of any major fluctuations in this ratio throughout the geologic time.

9. Origin of life on the earth • Life on the earth started in the ocean • Many possibilities explain the 1st organic compound on the Earth: • May come from meteorites, comets cosmic dust. • Hydrothermal vents • To have life organic matter on the Earth, the atmosphere must contain free oxygen for respiration. • What do you expect for the amount of free oxygen in the initial atomsphere?

11. The earliest atmosphere had 0.0 of oxygen due to the oxidation process during this time. Reduced nature of chemical substances in the volcanic rocks and gases, prevent any occurrence of free oxygen (O2) due its rapid consumption by oxidizing of these substances. • Evidence: all the volcanic rocks contain iron as Ferrous iron. • 8 FeO + 2 O2 4 Fe2O3 • Where did 1st life (plant) on Earth get free oxygen? • From the pyrite (Fe2S) formation: • FeO + S Fe2S + O2 (free oxygen for life usage)

12. From the photodissociation of water in the upper layers of the atmosphere. H2O + UV (ultraviolent radiations) → H2 + O2 • Life started in the ocean in an anaerobic environment, probably by this way Organic matter molecules

13. These conditions allow the formation of the organic matter by photosynthesis in the absence of chlorophyll. Once the 1st single life cell formed, the plants evolved producing free oxygen to the atmosphere by photosynthesis. • Photosynthesis process: 6H2O + 6CO2 + Energy C6H12O6 + 6O2

14. An experiment (Miller, 1952): Synthesis of organic carbon (amino acids). A mixture of water vapor, methane, ammonia and hydrogen was subjected to an electrical spark that provided the energy for synthesis. From Thurman, 1997.

15. 1st recorded Bacteria-cell like at 3.5 billion yrs • The earliest photosynthesis led to: • Increase the free oxygen to make up 21% of the present atmosphere which was one-tenth of the present day value. • Reduce the CO2 at present to 0.03% which was about 25% of the earliest atmosphere. What do you expect for the earliest atmosphere? • Sun became progressively hotter, so CO2 taken out from the atmosphere and stored on the ocean floor and on the continent as carbonate rocks. This led to gradual cooling of the earth. • Formation of the Ozone layer. • When plants evolved more and more, taking CO2 in their tissue the earth cooled to become pleasant for life. The study of fossil plants and animals could tell us more information about the earth's history.

16. Earth’s Rotation and the orbital forcing • Earth rotates around the sun with speed averaging 1000 mile/hour. Direction of rotation is towards the east. • The vertical axis of the earth is not perpendicular on the plane of the Ecliptic. It tilts by about 23.5 degree. • This tilt is responsible about the formation of the four seasons (summer, autumn, winter and spring) on the earth through the year. • Changes of the Earth’s Orbits around the sun resulted in many climatic cycles. These changes known as Orbital Forcing: • 1- Eccentricity (100,000 yrs) • 2- Precession (21,000 yrs) • 3- Obliquity (41,000 yrs)

17. Eccentricity The shape of the Earth's orbit around the Sun. It varies between more or less elliptical on a cycle of about 110,000 years. (This 110 000 year cycle is actually a combination of a 100 000 year cycle, and a much weaker one of 413 000 years.

18. Obliquity Axial tilt refers to the inclination of the Earth's axis in relation to its plane of orbit with the Sun.This inclination oscillates in a range of 21.8o and 24.4o. It takes the Earth about 41,000 years to move through this range. The difference in tilt affects where on the Earth receives the most and least solar radiation, but has global climatic consequences.

19. Precession Earth does not have a perfect spin about its axis. It wobbles, and this wobble is defined as precession. This Earth 'wobble' is with respect to the direction its rotational axis points. Within the framework of the stars, it represents a change of direction, from having the North pole pointing at the North Star, to having the North pole pointing at the star Vega.

20. Figure showing the changes of the Earth’s orbit and the tilt that result in changes in the insolation intensity from the sun. Consequently, three common climatic cycle are formed, called Eccentricity, Obliquity and Precession.