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Learning objectives. How old is the Earth? What is the Earth made from? What is Plate Tectonics? What happens at the different types of plate boundary?. How old is the Earth?. The Earth is…. 2 million years old. 100 million years old. 4600 million years old. 30 million years old.
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Learning objectives • How old is the Earth? • What is the Earth made from? • What is Plate Tectonics? • What happens at the different types of plate boundary?
How old is the Earth? The Earth is… 2 million years old • 100 million years old 4600 million years old 30 million years old
History of the Earth Look at this timeline. Where should each statement go? What do you notice? First flowers appear – 100 m India collides with Asia – 50 m Man (Homo sapiens) inhabits the Earth – 0.1 m Formation of the Alps – 30 m You were born! – 0.000013 m Dinosaur extinction – 65 m Industrial Revolution (UK) - 0.00015 m (figures are in ‘million years ago’) 4,000 3,000 2,000 1,000 today 4,600 million years ago
History of the Earth People (Homo sapiens) only appeared 100,000 years ago! Construct your own timeline using the following statements Big Bang! Dinosaurs die out Men-like apes Homo sapiens
4.6 billion years ago: Earth is formed, along with the other planets 4.2billion years ago : Continents begin to form 3.7 billion years ago: Earth's crust solidifies 3.5 billion years ago: First life appears in oceans 3.25 billion years ago: Photosynthesis begins in oceans 2.4 billion years ago: Oceans contain significant amounts of oxygen 1.9 billion years ago: First cells with nuclei appear in oceans 0.65 billion years ago: First multicellular organisms appear 0.5 billion years ago: First land plants with inner vessels 245 million years ago: Age of Dinosaurs begins 150 million years ago: Supercontinent breaking up; continents drifting apart 65 million years ago: Age of Dinosaurs ends, with mass extinction of 70% of all living things 3.5 million years ago: First proto-humans appear, in what is now Africa 100,000 years ago: First Homo sapiens appear 10,000 years ago: Recorded human history begins
Learning objectives • How old is the Earth? • What is the Earth made from? • What is Plate Tectonics? • What happens at the different types of plate boundary?
Under the above heading You will need to make a copy of the following diagram And you will need to add the notes that come with it The structure of The Earth
Learning objectives • How old is the Earth? • What is the Earth made from? • What is Plate Tectonics? • What happens at the different types of plate boundary?
What is continental drift? In 1912, a German scientist called Alfred Wegener proposed that South America and Africa were once joined together and had subsequently moved apart. He believed that all the continents were once joined together as one big land mass called Pangaea and this was intact until about 200 million years ago. The idea that continents are slowly shifting their positions is called continental drift.
Shapes of continents • Some continents fit together like a jigsaw. Africa South America Evidence for continental drift • Study of fossils • Similar fossils are found on different continents. • This is evidence that these regions were once very close or joined together. • Pattern of rocks • Similar pattern of rock layers on different continents is evidence that the rocks were once close together or joined.
What is plate tectonics? Wegener knew the continents had drifted but he couldn't explain how they drifted. It wasn't until the 1960's that geologists used ocean surveys to explain continental drift with the theory of Plate Tectonics. • What is Plate Tectonics? • The Earth's surface is made up of a number of large plates (like pieces of a jigsaw puzzle) that are in constant, slow motion. • The ocean floors are continually moving, spreading from the centre and sinking at the edges. • At the edges of these plates (plate boundaries) earthquakes and volcanoes occur. • Convection currents in the mantle move the plates. The source of heat driving the convection currents is radioactive decay which is happening deep in the Earth.
Plate names North American Eurasian Pacific Pacific African South American Indo-Australian Plate Nazca Antarctic
Plate names Can you name plates A and B? A African Plate B Indo-Australian Plate
Learning objectives • How old is the Earth? • What is the Earth made from? • What is Plate Tectonics? • What happens at the different types of plate boundary?
Tensional plate boundary At a tensional plate boundary, two plates move apart. As the two plates move apart, magma rises up to fill the gap. This causes volcanoes. However, since the magma can escape easily at the surface the volcano does not erupt with much force. Earthquakes are also found at constructive boundaries. An example of a constructive boundary is the Mid-Atlantic Ridge.
Mid-Atlantic ridge Sea Floor Spreading! Did you know that the ocean floor in the Atlantic is growing by 3cm per year? • Which of the following pairs of continents are moving further away from each other? • Europe and Africa • Europe and North America • South America and North America
6 metres 36 metres 200 metres 928 metres How fast do plates move? Tectonic plates move at different rates. The Nazca and Pacific plates are moving apart at a rate of 18cm per year while the Eurasian and North Americanplates are moving apart at a rate of 3cm per year. To the nearest metre, how far will the Nazca and Pacific plates have moved over the next 200 years?
Tensional plate boundaries mid-ocean ridge A ocean B oceanic crust mantle Where would you find older rocks – at A or at B?
Compressional plate boundary A compressional plate boundary is found where a continental plate meets an oceanic plate. The oceanic plate descends under the continental plate because it is denser. As the plate descends it starts to melt due to the friction caused by the movement between the plates. This melted plate is now hot, liquid rock (magma). The magma rises through the gaps in the continental plate. If it reaches the surface, the liquid rock forms a volcano.
Collision plate boundary Collision boundaries occur when two plates of similar densities move together (i.e. a continental plate and a continental plate). This causes the material between them to buckle and rise up, forming fold mountains. The Himalayas are an example of a chain of fold mountains. They have been formed by the Indo-Australian plate colliding into the Eurasian plate.
Passive/conservative plate boundary Passive plate boundaries exist where two plates do not directly collide but slide past each other along a fault (weakness). No volcanoes are found along these plate boundaries, but earthquakes do occur. An example of such a boundary is the San Andreas Fault in California.
Compressional plate boundary Match the labels to the letters. F E A B C D 1.oceanic plate 2. The oceanic crust sinks under the less dense continental crust. 3. The oceanic crust melts and rises. 5. explosive volcanoes 4. continental crust 6. mantle
