Unit 1B Natural hazards

2 Today What is a natural hazard? List them. What is the Earth’s structure? What are tectonic plates? How is the Earth changing? How are they linked to volcanoes and earthquakes?

3 Natural hazards A Natural Hazard is a natural event of unusual magnitude that people don't expect and cannot control. Natural hazards threaten people's lives and their activities and can forever change their ways of living. A natural hazard event can become a Natural Disaster when causes the destruction of people's property or their injury and/or death. In people's lifetime, at least one natural hazard will likely have some impact on their life. In the year 2001, natural hazards killed over 25,000 people and caused almost 40 billion Euros in damage worldwide. Unfortunately, the cost of natural hazards is increasing dramatically.

4 1. Geological hazards: Include hazards that are related to the structure of the earth. Geological hazards include  Avalanche  Earthquake  Landslides and mudflows  Volcanic eruption  Lahar 2. Atmospheric hazards: Include hazards that are caused by the air and weather Atmospheric hazards include  Flood  Tsunami  Drought  Cyclonic storms  Tornado  Wildfire hazard Go to aces.com/3+Hazardous+en vironments aces.com/3+Hazardous+en vironments Follow the link, read the page and return to do the quiz

5 The Structure of the Earth A thin crust km thick and not very dense A mantle – extends almost halfway to the centre, hot and dense A core – made of molten nickel and iron. Outer part is liquid and inner part is solid. Gets hot due to radioactive decay. The Earth is believed to be 4500 million years old

6 The structure of the earth inner core The inner core is in the centre of the earth and is the hottest part of the earth. The inner core is solid. It is made up of iron and nickel with temperatures of up to 5500°C. With its immense heat energy, the inner core is like the engine room of the Earth. outer core The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel. It is still extremely hot here, with temperatures similar to the inner core.

7 The structure of the earth mantle The mantle is the widest section of the earth. It has a diameter of approximately 2900km. The mantle is made up of semi-molten rock called magma. In the upper parts of the mantle the rock is hard, but lower down, nearer the inner core, the rock is soft and beginning to melt. crust The crust is the outer layer of the earth. It is a thin layer between 0-60km thick. The crust is the solid rock layer upon which

8 Plates and plate boundaries The earth's crust is broken up into pieces. These pieces are called plates. Heat rising and falling inside the mantle creates convection currents. The convection currents move the plates. The movement of the plates, and the activity inside the earth, is called plate tectonics. Plate tectonics cause earthquakes and volcanoes. The point where two plates meet is called a plate boundary. Earthquakes and volcanoes are most likely to occur either on or near plate boundaries.

9 These plates either:  Diverge – move towards each other or  Transform – move past each other  Converge – move towards each other What happens at the plate margins varies: 1. If the plates are diverging, then the plate boundaries move apart and new crust is created by the mantle welling up from below. This a constructive margin. 2. If the plates are moving past each other, then the margin is a conservative margin, as crust is neither made nor destroyed. 3. If the plates are moving towards each other, then one of 2 things can happen a) One plate moves under the other. This is a destructive margin (as some crust is reabsorbed into the mantle and destroyed) b) If two plates approach head on and fold up at the edges, this is a collision (zone) margin.

10 Don’t worry about the names of the plates – you do not need to know them! But take a few minutes to colour in examples of each type on your grey map.

11 Now a bit more about each plate – what is this one? The 2 plates move apart and molten rock or magma rises up to fill the gap and forms new crust. E.g. the mid- Atlantic Ridge, which Iceland forms part of – it moves about 3cm a year In 1967, there were undersea eruptions off Iceland – soon an island grew out of the sea - named Surtsey which is now 2.8km 2 and 178m above Sea Level. As you see, volcanoes occur but so does the odd gentle earthquake.

12 Which is this? These just slide past each other! As you see, this is a map of the famous San Andreas Fault on the West Coast of California. As the rock on either side is pressing so hard together, as the 2 plates pass, they judder – an earthquake. In 1906, some parts of the plate moved 6m! But you will not find volcanoes along these plates!

13 What is this called? These are usually found where an continental (land) crust is approaching an oceanic crust – the land crust is less dense and so floats over the oceanic crust which is forced down into the magma where it melts. This is called a subduction zone. Sometimes the edge of the continental crust is forced up at the edge by displaced magma which then escapes through volcanoes. So earthquakes and volcanoes here! The Andes Mountains were formed this way, along with the volcanoes, Chimborozo and Cotopaxi

14 The last one? Here 2 continental plates collide – neither plate can sink or be destroyed so fold mountains are formed. The Himalayas are growing at 5cm a year! And the Alps were an older version, but they have stopped growing now. No Volcanoes here either

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17 If the plates are moving, were the continents always where we see them today? No and there is lots of evidence for this The process is called continental drift Evidence for this: 1. Mountain chains match up 2. Fossils match up 3. The continents fit together like a jigsaw (not perfect because of erosion!)

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20 Continental Drift

21 Continental Drift

22 Continental Drift

23 Continental Drift

24 Can you see the UK, North America? Each colour represents a rock type – see how they fit together

25 Homework Research where recent volcanoes/ earthquakes have occurred – try for at least 2 of each. Use the tables provided to add small location map, the name and place – the Richter Scale (if earthquake), the damage done and any other notes. I have given you several links on the wikis (they are on both) but I am sure there are other sites too. Be sure to keep this safe as looking at recent events can be asked for in the exam