Change in the Earth - Science Physics G7

Science Physics

1. 6.4 Changes In the Earth Earth Physics 7th Grade

2. Explain how fold mountains and volcanoes are formed Explain how earthquakes happen. Learning Objectives

3. Geological changes Movement of plates Fold mountains, Volcanoes and Earthquake SW Geological change happens most frequently at plate boundaries. It creates three types of plate boundaries. These events are happened when plates are moving. You will do SW 01 02 03 04 Table of Contents

4. Geological change The plates where tectonic plates meet are called PLATE BOUNDARIES. 01

5. GEOLOGICAL CHANGE Happens Why? Geological change happens most frequently. Because tectonic plates are moving. Time taken Some changes are very slow, it takes over millions of years. But, some are very sudden & violet. 01 02 03

6. —Pacific Ring of Fire “There are many geological changes and events, such as volcanic eruptions and earthquakes. This area is often called the …”

7. Movement of plates The movement of tectonic plates creates three types of plates boundaries. 02

8. Three types of boundaries Plates moving together Plates moving apart Plates sliding past 1 2 3

9. Plates moving together One plate may slide underneath the other one. This is called subduction. The rocks in the Earth’s crust melt as they move into the mantle. They become part of the mantle.

10. Plates moving together

11. Plates moving apart As tectonic plates drift away from each other, they break and crack when they become too thin. Lava (liquid rock) erupts from the mantle and hardens to form new crust with new rocks. This causes a volcano.

12. Plates moving apart

13. Plates moving apart

14. Plates sliding past Why? There Because the plates are very large and heavy, there is a lot of friction between the plates. Over the years, this makes the plates stick together. is always force on the tectonic plates, so the pressure builds up and eventually the pressure causes violent movement. This is an earthquake .

15. Plates sliding past

16. Three types of movement of plates

17. Events caused by movement of plates Earthquakes Volcanoes Fold mountains

18. Fold Mountain Sometimes, when tectonic plates move together, the rocks crumple and fold upwards. The mountains that this produces are called fold mountains. This can happen under the ocean or on land. The newest fold mountains are between 10 and 25 million years old. The oldest fold mountains are more than 200 million years old

19. Fold Mountains

20. Fold mountains the Himalayas in Asia and the Rocky Mountains in North America, the Ural Mountains in Russia.

21. Volcanoes Volcanoes are usually formed at the plate boundaries when magma from the mantle rises through cracks in the Earth’s crust

22. Others At the Earth’s surface, magma erupts to form lava flows and ash deposits. Magma is the name for liquid rock when it is underground. Lava is the name for liquid rock when it is on the surface. The lava and ash harden as they cool to form new rocks. So, each time the volcano erupts, it gets bigger

23. Sometimes, if the magma is thick, and contains dissolved gas, pressure builds up and the eruption is violent. Gases and rock shoot up through the opening. Violent eruptions can even cause avalanches and earthquakes – and tsunamis if the volcano is close to the sea.

24. Volcanoes Some volcanoes are active and may erupt at any time. Some volcanoes are inactive or dormant , which means they have not erupted for a very long time. Other volcanoes are extinct , which means they will not erupt again.

25. A powerful eruption at Anak Krakatau volcano, Indonesia. Part of the volcano was blown off into the sea, causing a tsunami.

26. Earthquakes Violent The size Some earthquakes are extremely violent and cause a lot of damage. The size or magnitude of the earthquake depends on the size of the faults at the plate boundaries, and how far the rocks move when the earthquake happens. Light The largest Some are so slight that they only register on scientific instruments In the largest earthquakes, the rocks can move tens of metres in seconds.

27. Earthquakes can cause damage to roads and buildings.

28. That’s all