Download to read offline
More Related Content
Similar to Origin of Atmosphere.pptx
More from sapna kinattinkara
Origin of Atmosphere.pptx
- 1.
- 2. • Earth isbelieved to have formed about 5 billion years ago. • In the first 500 million years, a dense atmosphere emerged from the vapor and gases that were expelled during degassing of the planet’s interior. – During the cooling of the earth, gases and water vapour were released from the interior solid earth. This started the evolution of the present atmosphere. This process is called degassing.
- 3. • These gasesmay have consisted of hydrogen (H2), water vapor, methane (CH4) , and carbon oxides. • Prior to 3.5 billion years ago the atmosphere probably consisted of carbon dioxide (CO2), carbon monoxide (CO), water (H2O), nitrogen (N2), and hydrogen. • The hydrosphere was formed 4 billion years ago from the condensation of water vapor, resulting in oceans of water in which sedimentation occurred.
- 4. • The mostimportant feature of the ancient environment was the absence of free oxygen. • Evidence of such an anaerobic reducing atmosphere is hidden in early rock formations that contain many elements, such as iron and uranium, in their reduced states. • Elements in this state are not found in the rocks of mid-Precambrian and younger ages, less than 3 billion years old.
- 5. • One billionyears ago, early aquatic organisms called blue-green algae began using energy from the Sun to split molecules of H2O and CO2 and recombine them into organic compounds and molecular oxygen (O2). • This solar energy conversion process is known as photosynthesis. Some of the photosynthetically created oxygen combined with organic carbon to recreate CO2 molecules. • The remaining oxygen accumulated in the atmosphere, touching off a massive ecological disaster with respect to early existing anaerobic organisms. • As oxygen in the atmosphere increased, CO2 decreased.
- 6. • High inthe atmosphere, some oxygen (O2) molecules absorbed energy from the Sun’s ultraviolet (UV) rays and split to form single oxygen atoms. • These atoms combining with remaining oxygen (O2) to form ozone (O3) molecules, which are very effective at absorbing UV rays. • The thin layer of ozone that surrounds Earth acts as a shield, protecting the planet from irradiation by UV light.
- 7. • The amountof ozone required to shield Earth from biologically lethal UV radiation, wavelengths from 200 to 300 nanometers (nm), is believed to have been in existence 600 million years ago • . At this time, the oxygen level was approximately 10% of its present atmospheric concentration. • Prior to this period, life was restricted to the ocean. • The presence of ozone enabled organisms to develop and live on the land. • Ozone played a significant role in the evolution of life on Earth and allows life as we presently know it to exist.
- 8. 3 Phases ofAtmosphere Formation • Just formed Earth: Like Earth, the hydrogen (H2) and helium (He) was very warm. • These molecules of gas moved so fast they escaped Earth’s gravity and eventually all drifted off into space.
- 9. • Earth’s originalatmosphere was probably just hydrogen and helium because these were the main gases in the dusty, gassy disk around the Sun from which the planets formed. • The Earth and its atmosphere were very hot. Molecules of hydrogen and helium move really fast, especially when warm. • Actually, they moved so fast they eventually all escaped Earth’s gravity and drifted off into space.
- 11. • Young Earth:Volcanoes released gases H2O (water) as steam, carbon dioxide (CO2), and ammonia (NH3). • Carbon dioxide dissolved in seawater. Simple bacteria thrived on sunlight and CO2. By- product is oxygen (O2).
- 12. • Earth’s “secondatmosphere” came from Earth itself. There were lots of volcanoes, many more than today because Earth’s crust was still forming. The volcanoes released – steam (H2O, with two hydrogen atoms and one oxygen atom), – carbon dioxide (CO2, with one carbon atoms and two oxygen atoms), – ammonia (NH3, with one nitrogen atom and three hydrogen atoms).
- 14. • Current Earth:Plants and animals thrive in balance. • Plants take in carbon dioxide (CO2) and give off oxygen (O2). • Animals take in oxygen (O2) and give off CO2. Burning stuff also gives off CO2.
- 15. • Much ofthe CO2 dissolved into the oceans. Eventually, a simple form of bacteria developed that could live on energy from the Sun and carbon dioxide in the water, producing oxygen as a waste product. • Thus, oxygen began to build up in the atmosphere, while the carbon dioxide levels continued to drop. • Meanwhile, the ammonia molecules in the atmosphere were broken apart by sunlight, leaving nitrogen and hydrogen. • The hydrogen, being the lightest element, rose to the top of the atmosphere and much of it eventually drifted off into space.
- 17. • Now wehave Earth’s “third atmosphere,” the one we all know and love—an atmosphere containing enough oxygen for animals, including ourselves, to evolve.
- 18. Formation of Hydrosphere •The hydrosphere formed approximately 4.5 billion years ago around the same time as the atmosphere. • When the planet formed, there were high levels of volcanic activity, which expelled a huge amount of water vapor into the air. • Additionally, some minerals within the deeper layers of earth contained water.
- 19. • As Earthcooled, the water vapor in the atmosphere condensed and fell as rain. • These cooler conditions meant that when water reached the surface, it would not evaporate instantly and could accumulate. • These cooler conditions also meant that water released by minerals in the crust could accumulate on the surface as well. • This marked the formation of the early hydrosphere. • Over time, water began to collect in large basins forming oceans and seas.
- 20. CONCEPT OF MINERALSAND ROCKS • Rocks and the minerals are known to be the building blocks of our active planet. • They are the reason how the landscapes are formed and these provide all the necessary valuable resources needed within our environment.
- 21. What are Rocks? •A Rock is an inorganic, solid and natural substance without any specific atomic structure or chemical composition. • It is simple to remember that rocks are made up of two or more minerals. • Examples of rocks involve limestone, granite, marble, slate and sandstone. • Each of these rocks consists of different minerals that can be mixed up with the rock through different geologic processes.
- 22. • Let’s considergranite. It mostly consists of three minerals namely: quartz, mica and feldspar. • All these minerals exist in nature but mixed up with the rock. • Sometimes you see big chunks of one of these minerals in granite, but when you take that stone as a whole, you have to call it rock.
- 24. What are Minerals? •A mineral is defined as a natural, inorganic solid substance which has a crystalline structure with a particular chemical composition. • A mineral is said to possess different chemical composition which defines it crystalline shape and form. • Whereas, the rock which is said to be comprised of several minerals, is generally classified based upon the process of its formation.
- 26. Differences between Rocksand Minerals
- 27. Types of Rocks •There are three types of rocks: • Igneous Rocks • Sedimentary Rocks • Metamorphic Rocks
- 28. Formation of IgneousRocks • Molten materials are found below the earth’s crust and are normally subjected to extreme pressure and temperatures – up to 1200° Celsius. • Because of the high temperatures and pressure changes, the molten materials sometimes shoot up to the surface in the form of volcanic eruption and they cool down to form volcanic or extrusive igneous rocks.
- 29. • Alternatively, someof the molten materials may cool underneath the earth’s surface very slowly to form plutonic or intrusive igneous rocks. • It is because of the extreme heat levels and changes in pressure that igneous rocks do not contain organic matter or fossils. • The molten minerals interlock and crystallize as the melt cools and forms solid materials.
- 30. • In thelong-run, the melt forms a cool hard rock made up of crystals with no open spaces and don’t exhibit any desirable grain alignment. • The rocks may be made up entirely of one mineral or various minerals, and their sizes are determined by the cooling process. • Rapid cooling results in smaller crystals while slow cooling results in large crystals.
- 31. Types of IgneousRocks • Igneous rocks are of two types, • intrusive (plutonic rocks) and extrusive (volcanic rocks).
- 32. 1. Intrusive IgneousRocks • Intrusive igneous rocks are formed when the magma cools off slowly under the earth’s crust and hardens into rocks. • Gabbro and granite are examples of intrusive igneous rocks. • Intrusive rocks are very hard in nature and are often coarse-grained.
- 33. 2. Extrusive IgneousRocks • Extrusive igneous rocks are formed when molten magma spill over to the surface as a result of a volcanic eruption. • The magma on the surface (lava) cools faster on the surface to form igneous rocks that are fine-grained. • Examples of such kind of rocks include pumice, basalt, or obsidian.
- 34. Examples of IgneousRocks • There are more than 700 known types of igneous rocks and most of them are formed under the earth’s crust since volcanic events are not all that frequent. • On this basis, we are going to look at the commonly identified types of igneous rocks, both intrusive and extrusive. They include:
- 35. 1. Granite • Granitesare the light-colored and coarse-grained igneous rocks. • They are intrusive rocks and they contain three major minerals including feldspar, mica and quartz. • They appear pinkish, gray or tan depending on the grain sizes and concentrations and grain sizes of the three minerals. • Granites are often used in construction activities because of its strength and presence in great quantities.
- 36. 2. Gabbro • Gabbrosare the dark-colored and coarse- grained igneous rocks. • They are intrusive rocks and they are made up of mineral elements including pyroxene, feldspar, and sometimes olivine. • They appear grey in color with minute dark spots all over them.
- 37. 3. Basalt • Basaltsare the dense dark-grey colored and fine-grained igneous rocks. • They are extrusive and are chiefly composed of plagioclase and pyroxene. • They are the commonest type of solidified lava. • Basalts are also frequently used in building and construction.
- 38. 4. Diorite • Dioritesare the coarse-grained igneous rocks just like the Gabbros and Granite. • They are intrusive and contain a mixture of minerals including hornblende, pyroxene, feldspar and sometimes quartz. • They appear light-colored with some dark spots.
- 39. 5. Andesite • Andesitesare light grey-colored and fine- grained igneous rocks. • They are extrusive rocks which are mainly made up of plagioclase minerals mixed up with biotite, pyroxene, and hornblende.
- 40. Formation of Metamorphicrocks • Metamorphic rocks are the rocks formed from other rocks. • They are sedimentary or igneous rocks that have undergone changes as a result of extreme pressure and heat. • The name defines their formation whereby ‘meta’ means change and ‘morph’ means ‘form.’ • Hence, metamorphic rocks are those whose forms have been changed through a geological process such as large tectonic movements and magma intrusions.
- 41. • Large tectonicmovements and magma intrusions create earth movements and subsequently cause the pre-existing rocks to move and shift. • In turn, the movements subject other rocks buried deep below the earth’s surface to extreme pressure and heat which contributes to changes and assemblage of the rocks texture, mineralogy, and chemical composition.
- 42. • The changestypically modify the rock’s crystal type and sizes and may also subject the rocks to further radical changes. • Metamorphic processes come about at heats between 150° and 795° Celsius with the capability of producing high energy that can break and reform the chemical compositions of the rocks. • Pressure from the overlying rocks also increases the process of transformation.
- 43. • The heatfrom magma and friction along fault lines is the major contributor of the heat that brings about the rock changes. • Even though the rocks do not actually melt, some mineral groupings redistribute the elements within the original minerals to form new compositions of minerals that are more stable at the new temperatures and pressures.
- 44. • The intensetemperature gradient between the country rocks and the surrounding molten magma is the driving factor for the changes in texture and chemical composition. • As a result, the original rocks are transformed into metamorphic rocks. • Metamorphic rocks formed from direct magma heating and intrusions are termed as thermal or contact metamorphic rocks.
- 45. • Those formedas a result of widely distributed pressure and temperature changes induced by tectonic movements are known as regional metamorphic rocks.
- 46. Types of MetamorphicRocks • There are two main types of metamorphic rocks. • These are Foliated metamorphic rocks and Non-foliated metamorphic rocks.
- 47. 1. Foliated MetamorphicRocks • Foliated metamorphic rocks are formed from direct exposure to pressure and heat. • They are the most vital and largest groupings of metamorphic rocks. • Foliated metamorphic rocks have four distinguishable types of aligned textures and they normally have a banded or layered appearance.
- 48. • Examples includeslate, gneiss, phyllite, and schist. • Non-foliated are formed as a result of tectonic movements or direct pressure which makes their formation highly dependent on their pre-existing conditions.
- 49. 2. Non-foliated MetamorphicRocks • Non-foliated metamorphic rocks do not have a banded or layered appearance. • The extensively known example of non- foliated metamorphic rock is a marble. • Other examples include quartzite, hornfels, and novaculite.
- 50. Examples of MetamorphicRocks • 1. Hornfels • Hornfels is a fine-grained metamorphic rock formed by the action of heat on clay rocks, known as contact metamorphism. • It has a non-foliated metamorphic rock that has no specific composition. • Hornfels are heated when near a heat source such as a sill, dike, or magma chamber.
- 51. 2. Amphibolite • Amphiboliteis non-foliated metamorphic rock that is composed chiefly of plagioclase and amphibole (hornblende), frequently with very little quartz. • Amphibolite forms under conditions of directed pressure and high viscosity through the process of recrystallization.
- 52. 3. Gneiss • Gneissis a foliated metamorphic rock made up of granular mineral grains. • It contains a lot of feldspar minerals and bands of quartz and sometimes mica. • It normally has a banded appearance and is sort of laminated. • It appears similar to granite.
- 53. 4. Novaculite • Novaculiteis a hard, fine-grained, dense, siliceous rock. • It is non-foliated metamorphic rocks known to break with a conchoidal fracture. • It forms in marine environments from sediment deposits where organisms like diatoms plentiful in water – the single-celled algae that secret hard shells made up of silicon dioxide.
- 54. 5. Marble • Marbleis among the non-foliated metamorphic rocks produced from the metamorphism of dolostone or limestone. • It takes high polish and is often used for sculpture and as building material. • Marble is mainly composed of calcium carbonate.