Volcanoes Exploding mountains? But before that – a bit of revision from last week and I want EVERYONE to have a go!

As __ is to ___ then ___ is to ? Why? As H is to L, then F is to ? What is the rule? F

As B is to N, then D is to ? What is the rule? As G is to E, then A is to ? What is the rule? As V is to J, then Y is to ? What is the rule? F

Which is the Odd One Out? And why? Because it is not ……. 1. F, J, N 2. W, T, Z 3. U,L,R F

VOLCANOES The word "volcano" comes from the little island of Vulcano in the Mediterranean Sea off Sicily (Italy). Centuries ago, the people living in this area believed that Vulcano was the chimney of the god Vulcan ( he was the blacksmith of the Roman gods -- he made things out of metals). They thought that the hot lava pieces and clouds of dust erupting from Vulcano came from Vulcan's furnace as he made thunderbolts for Jupiter, king of the gods, and weapons for Mars, the god of war. In Polynesia the people attributed eruptive activity to the beautiful but wrathful Pele, Goddess of Volcanoes, whenever she was angry or spiteful. Today we know that volcanic eruptions are not super-natural but can be studied and interpreted by scientists.

So, What is a volcano? Volcanoes are mountains, but they are very different from other mountains; volcanoes are built by the accumulation of their own eruptive products -- lava, bombs (hardened lava blobs), ashflows, and tephra (airborne ash and dust). A volcano is most commonly a cone shaped hill or mountain built around a vent that connects with pockets of molten rock (magma) below the surface of the Earth. The term volcano also refers to the opening or vent through which the molten rock and associated gases are expelled.

As you heard last week… Volcanoes generally form along plate margins Either where the plates are approaching each other and one is sliding under the other – destructive margins Or where they are moving away from each other – constructive margins There are a few exceptions – called hot spots – where the magma bursts through a particularly thin bit of oceanic crust, for example in Hawii.

Distribution of some of the world’s major volcanoes Ring of Fire

How do they form? This one is forming on a destructive plate As the oceanic crust slips beneath the continental plate, some of the magma gets trapped above. This is force out through any crack it can find in the continental plate. Violà – you have a volcano!

Which of these are volcanoes? They all are!

Types of volcano They all were !

Shield Volcanoes Broad, slightly domed-shaped Made of layers of frozen lava May be 100s of km across and have a large crater Produced by mild eruptions of large volumes of lava Non-explosive eruptions Mauna Loa on Hawaii is a good example

Cinder Cone Volcanoes Moderately explosive Example: Paricutin (Mexico) Made of loose grainy cinders and no lava Steep slope angle Rather small size about 1 km across with a small crater Frequently occur in groups Moderately explosive Example: Paricutin (Mexico)

Composite Volcanoes Most are located adjacent to the Pacific Ocean (e.g., Fujiyama, Mt. St. Helens) Large, classic-shaped volcano (1000’s of ft. high & several miles wide at base) with a small crater Composed of layers of lava flows with layer of cinder and ash in between May have very explosive eruptions

A composite volcano

Comparing sizes

A: Mount Rainier, Washington State in western USA Which type is this? A: Mount Rainier, Washington State in western USA

Which type is this? B: Paricutin, Mexico

Which type is this? C : Mauna Loa, Hawaii

Which type is this? D: Papua New Guinea

E: Popocatepetl, Mexico Which type is this? E: Popocatepetl, Mexico

How did you do? A = composite (Mount Rainier, WA) B = cinder cone (Paricutin, Mexico) C = shield (Mauna Loa, Hawaii) D = cinder cone (Papua New Guinea) E = composite (Popocatepetl, Mexico)

Types of Lava Volcanic eruptions may be quiet outflows of lava which are so peaceful that one can stand close enough to toss in pebbles or so explosively violent that they blow mountains apart and blast everything within a hundred miles to smithereens (not recommended for close observation).

Two types of lava (they are called Pahoehoe and Aa in Hawaii) Pahoehoe lavas are thin. They flow smoothly and are often formed by small volumes of hot, fluidbasalt. The higher the volume of lava emitted the faster the current. Pahoehoe flows move forwards in tongues or lobes and are characterized by a glassy, plastic skin. They may embrace obstacles at a rate of about 50m an hour. When the pahoehoe lava flow cools, it often solidifies to a smooth surface. Aa flows are emitted from the vent at high rates ranging to 50km an hour, often with much lava fountaining. They are characteristic of viscous magmas. Aa flows are animated with sporadic bursts of energy. They may push down houses, walls and forests. However, the hallmark of aa lava flows is the very rough surface it produces when it cools and solidifies.

Other volcanic landforms Calderas Steep-walled depressions at the summit Size generally exceeds 1 km in diameter Example Santorini in Greece

Caldera

Volcanoes and climate Explosive eruptions emit huge quantities of gases and fine-grained debris into the atmosphere which filter out and reflect a portion of the incoming solar radiation Examples of volcanoes affecting climate Mount Tambora, Indonesia – 1815 Krakatau, Indonesia – 1883 Mount Pinatubo, Philippines - 1991

VOLCANIC ACTIVITY ACTIVE - A volcano that has erupted in the recent past and is expected to erupt again. Any names? DORMANT - A “sleeping” volcano. A volcano that has not erupted in the recent past, but could erupt again. One in Yellowstone has not erupted fro 640,000 years BUT there are still earthquakes and steam emissions so it could! EXTINCT - A volcano that is not expected to erupt again. This is because there is no longer a source of magma. Castle rock in Edinburgh is an example

There is a zondle on the wiki page But before that homework!

Homework Choose an active volcano (or at least one that has erupted in the last 20 years or so) Find out its name and where it is – I will send you a world map to move a X to the right spot. Find out which sort of volcano it is – shield, composite or cinder cone Find out 4 other things about it * You will also need to visit the Zondle on the zondle website to record a score – same rules as last week.

Suggestions for your other 4 things A picture of your volcano Geographic setting: Is it on an island or in a mountain range? Is it near towns or cities or is it isolated When did your volcano last erupt? what do you know about it? Was the eruption hazardous to people? What happened? If the volcano erupts again, what are the possible hazards? Does it pose a threat now? What are 2 cool facts about your volcano?