KS4 Changes to the Earth and atmosphere

1. KS4 Changes to the Earth and atmosphere

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3. The Atmosphere

4. The Earth was formed about 4500 million years ago. The very first atmosphere mainly consisted of hydrogen and helium gases. Frozen giant planets like Saturn and Jupiter still have atmospheres like this but on the warmer, smaller Earth these light gases were largely lost into space. Jupiter Saturn In the beginning -

5. During the first billion years on Earth there was intense volcanic activity. This produced the next early atmosphere. It would have contained large quantities of carbon dioxide (CO2), along with methane (CH4) , and ammonia (NH3). This is rather like the atmosphere on Mars and Venus today. The Earth’s atmosphere would also have contained water vapour which condensed to form the oceans. Mars Venus The early atmosphere

6. Carbon dioxide reacted with rocks and much became trapped in them. The evolution of algae some 3000 million years ago, and subsequently plants which successfully colonised the Earth’s surface, led us towards the present atmosphere. Their photosynthesis replaced carbon dioxide with oxygen. Over a period of time billions of tonnes of carbon dioxide became locked up in fossil fuels. Earth Photosynthesis increased oxygen levels Oxygen levels increase

7. As oxygen levels rose atmospheric ammonia (NH3) reacted with oxygen(O2) to form water(H2O) and nitrogen (N2) Also, living organisms, including denitrifying bacteria, broke down nitrogen compounds releasing more nitrogen into the atmosphere. And so the atmosphere headed towards a composition that has remained fairly constant for the last 200 million years. Nitrogen makes an appearance

8. Oxygen normally exists as pairs of atoms (O2). Oxygen can, however, turn into another form that has three atoms joined together. This is ozone (O3). As oxygen levels rose, so did the amount of ozone. This layer of ozone in the atmosphere filters out harmful ultraviolet rays from the sun. This will have allowed new organisms to evolve and survive. Earth Ozone – a vital filter 3O2 2O3 Oxygen ozone Harmful UV rays stopped with ozone layer Harmful UV rays reach Earth’s surface without ozone layer

9. Activity Copy the timeline and arrange the blue boxes in appropriate places along the line. Now 4500 million 3000 million 2000 million 1000 million 500 million 200 million H2O N2 O2 No gases CO2 NH3 CH4 H2 and He Volcanoes Algae Plants

10. All positions are approximate Answer No gases Plants Algae Volcanoes Now 4500 million 3000 million 2000 million 1000 million 500 million 200 million O2 N2 H2O CO2 NH3 CH4 H2 and He

11. What was the main gas in the atmosphere around 3500M years ago? Where did this gas come from? What process led to reduction in CO2 levels? What gas protects life from harmful UV radiation? What % of the present atmosphere is oxygen? Activity Carbon dioxide Volcanoes Photosynthesis Ozone 21%

12. Use the graph to estimate the answers. How long ago was the atmosphere 75% CO2? How long ago were the CO2 and N2 levels in the atmosphere equal? How long ago was the atmosphere 50% nitrogen? Activity 100% carbon dioxide nitrogen 50% Composition percentage oxygen now 0% 5000 3000 0 Time (millions of years) Approx 4,000M Approx 3,300M Approx 2,000M

13. Find the words in the word-search Write a sentence about how each has played a part in the evolution of the Earth’s atmosphere. Activity Ammonia Carbon dioxide Helium Hydrogen Methane Nitrogen Oxygen Ozone Photosynthesis Volcano

16. Over millions of years the carbon cycle has maintained a constant, low percentage (approx. 0.03%) of carbon dioxide in the atmosphere. In 1860, the CO2 level was about 289 ppm (parts per million). Here is a table showing the CO2 levels over a recent 10 year period. Carbon dioxide and temperature • What percentage change is this and does it matter?

17. From air trapped in Antarctic ice, we have a good idea of CO2 concentrations going back 160,000 years. 200ppm CO2 300ppm CO2 Greenhouse effect We also know the temperatures over the same period. The very warm interglacial period of 130,000 years ago was accompanied by CO2 levels of around 300 ppm. The previous great Ice Age had CO2 levels around 200 ppm. Which label goes with each picture?

18. Normally the Earth absorbs heat and emits heat at the same rate. Because of this the temperature remains constant. Certain gases, like CO2 and methane, act like a greenhouse. They let heat in but do not let it out. This means: the more CO2 there is, the hotter planet Earth is! Earth More CO2 balanced same temp Earth Greenhouse effect Heat loss Heat from sun Heat loss Heat from sun hotter And hotter! And hotter

19. The Earth’s Structure

20. The Earth’s Structure Beneath the atmosphere the Earth consists of 3 main layers:

21. The temperature is high and the outer core is molten. Towards the centre high pressure makes the inner core solid. Intense heat is generated in the inner core by decay of radioactive elements like uranium. 1300 km 1110 km 3000 km The core The core extends to about half the radius of the Earth. It is made mostly from iron and nickel and is where the Earth’s magnetic field comes from. It is very dense. 5500 C Inner core Outer core

22. The mantle extends outwards from the core to the crust: a distance of about 2,900 km. It is mostly a semi-molten liquid upon which the Earth’s crust floats. The heat coming from the core generates convection currents in the viscous mantle that cause the crust above to move. 2900km The mantle Mantle

23. The crust is the thin layer of rock at the surface upon which we live. Eight elements make up over 98% of the Earth’s Crust – although they are virtually entirely in the form of compounds. % 20-60 km The crust Crust

24. I am dense, very hot, made mostly of solid iron and nickel. I’m iron and nickel too, but I’m liquid. I’m really very thin and am mostly silicon, oxygen and aluminium I’m a viscous semi-solid with convection currents circulating in me. I just hang around on the outside. What am I? Inner core Outer core Crust Mantle Atmosphere

25. Attach labels to the correct part of the diagram. Atmosphere Outer core Crust Mantle Inner core

26. Plate Tectonics

27. The crust is made of about twelve plates. These are like big rafts floating on the semi-molten mantle. Convection currents within the mantle cause the plates to move. Although they only move about 2 cm/year this can have huge effects over long periods of time. Tectonic plates

29. When two oceanic plates move apart molten rock rises to the surface. sea floor spreading oceanic plate magma rising Sea floor spreading

30. On average, the plates only drift about 2cm/year. However 2cm multiplied by a million is a long way! Scientists think the continents were originally all together in a super-continent called Pangaea. Over millions of years they have drifted to their present positions on the floating tectonic plates. Pangaea Millions of years Continental Drift

31. Continental Drift

32. The theory is supported by several pieces of evidence. For example, if we consider Africa and South America there is: The “jig-saw fit” The similarities in the rock layers from Africa and South America. Similarities in the type and age of fossils. Evidence of related species that definitely did not swim the Atlantic Ocean! Jig Saw fit Similar rocks and fossils Evidence for Continental Drift

33. Plate boundaries

34. volcanoes result from the rising magma (melted oceanic plate) volcano oceanic plate magma rising continental plate Effects at Plate Boundaries When a continental plate and an oceanic plate meet, the effects include: • plates juddering past each other producing earthquakes • the continental plate buckles upwards whilst the oceanic plate subducts (goes underground)

35. Find the words and write a sentence about how each one has something to do with plate tectonics. Drift Earthquake Fossil Jigsaw Magma Pangaea Plates Subduct Volcano Activity

36. Rocks

37. There are three main types of rocks: Igneous - formed when molten rock cools. Sedimentary – formed by the “cementing together” of small grains of sediment. Metamorphic – rocks changed by the effect of heat and pressure. All of these are involved in a continuous flow of rock from the surface underground only to emerge again later as part of the on-going rock cycle. Types of rocks

38. These are rocks formed by the cooling of molten rock (magma.) volcano magma Igneous rocks Magma cools and solidifies forming igneous rocks.

39. Igneous rocks divide into two main groups: Intrusive igneous Extrusive igneous. • Intrusive igneous rocks, like granite, are formed when magma solidifies within the ground. • Extrusive igneous rocks, like basalt, are formed when magma solidifies above the ground. Types of igneous rocks

40. The more slowly a rock changes from liquid to solid the bigger the crystals grow. • Intrusive igneous rocks that cool really slowly can have very big crystals. Extrusive igneous rocks that cool really quickly can have a glassy appearance. Igneous rocks and crystal size Intrusive igneous rocks, like granite, usually have clearly visible crystals. Extrusive igneous rocks, like basalt, have crystals that are usually small.

41. Surface rocks seem to be gradually reduced in size by weathering processes. Chemical weathering is when chemicals, such as those in acid rain, ‘eat’ away certain rocks. Physical weathering is to do with the rocks being broken down by the action of wind, rain and sun. For example, during the freezing and thawing of water in the cracks of rocks, the expansion of water makes the rocks splinter. The small broken fragments wash into rivers and, eventually, reach the sea where they settle as sediment. Chemical and Physical Weathering

42. Sedimentary Rocks are rocks formed when particles of sediment build up and are “cemented together” by the effect of pressure and minerals. Rocks are broken up by the action of weather sea Sedimentary rocks Sedimentary rocks Fragments washed to the sea

43. Sedimentary Rocks tend to have visible grains of sediment. Sometimes they contain fossils. They are usually softer than igneous rocks. Examples of sedimentary rocks are sandstone and mudstone. Getting older Sedimentary rocks Sandstone is formed from the cementing together of grains of sand.

44. Metamorphic rocks are formed by the effect of heat and pressure on existing rocks. This can greatly affect the hardness, texture or layer patterns of the rocks. Pressure from surface rocks metamorphic rock forming here Magma heat Metamorphic rocks

45. Marble, slate and schist are metamorphic. Limestone is a rock often formed from the sediment of shells. Temperature and pressure cause the rock to reform as small crystals that are much harder. It is used as a hard and decorative stone in buildings, sculptures etc. Slate is formed when pressure squeezes mudstone into plate like grey sheets. It is used in roofing. Schist and mica are formed when mudstone is subjected to very high temperatures as well as pressure. Again they contain layers which is typical of many (not all) metamorphic rocks. Metamorphic rocks

46. Match the rock with the correct description. Give an example of this type of rock. Activity

47. The rock cycle

48. Crack the code! What should this really say? (Giant hewer)leads to fragments collecting in the sea and forming (am seen dirty)rocks such aschalk, (sum to end)and(and so nest). Heat and(perusers)can lead to(a chem import)rocks such as(stale)and(ambler). Some of these willmelt and eventually cool as they approach the surface to form (I ruin vets)(go in use)rocks such as (get rain). Activity Weathering sedimentary mudstone sandstone pressure metamorphic slate marble intrusive igneous granite

49. What gases would have formed the original atmosphere around planet Earth? Hydrogen and helium Oxygen and nitrogen Methane and ammonia Carbon dioxide and water

50. What gases form the majority of the present atmosphere around planet Earth? Hydrogen and helium Oxygen and nitrogen Methane and ammonia Carbon dioxide and water