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Volcanoes Earth Science Chapter 8 Scholz. What is a Volcano One dictionary meaning: volcano is a vent in the earth's crust through which rock or lava.

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Presentation on theme: "Volcanoes Earth Science Chapter 8 Scholz. What is a Volcano One dictionary meaning: volcano is a vent in the earth's crust through which rock or lava."— Presentation transcript:

1 Volcanoes Earth Science Chapter 8 Scholz

2 What is a Volcano One dictionary meaning: volcano is a vent in the earth's crust through which rock or lava is ejected. Most volcanologists disagree with both of these dictionary definitions. Another, a volcano is a cone-shaped hill or mountain built around a vent.

3 Volcanic Eruptions come in two varieties.Volcanic Eruptions come in two varieties. Non-explosiveNon-explosive ExplosiveExplosive Volcanic Eruptions

4 Non-Explosive Eruptions Non Explosive Eruptions are also called Lava FlowsNon Explosive Eruptions are also called Lava Flows Lava can spray in the airLava can spray in the air Lava can also flow like a riverLava can also flow like a river

5 Explosive Eruptions In an Explosive Eruption hot debris, gas, & molten rock is blown into the airIn an Explosive Eruption hot debris, gas, & molten rock is blown into the air Solid rock is also thrown into the airSolid rock is also thrown into the air Explosive Volcanoes actually shrinkExplosive Volcanoes actually shrink

6 Parts of a Volcano

7 What comes out? LavaLava –Blocky –Pahoehoe –Aa –Pillow Pyroclastic MaterialPyroclastic Material –Blocks –Bombs –Lapilli –Ash

8 Lava: Pahoehoe Pahoehoe is a Hawaiian term for basaltic lava that has a smooth, hummocky, or ropy surface. A pahoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. The surface texture of pahoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture

9 `A`a (pronounced "ah-ah") is a Hawaiian term for lava flows that have a rough rubbly surface composed of broken lava blocks called clinkers. The incredibly spiny surface of a solidified `a`a flow makes walking very difficult and slow. Lava: Aa

10 When basalts erupt underwater, they commonly form pillow lavas, which are mounds of elongate lava "pillows" formed by repeated oozing and quenching of the hot basalt. First, a flexible glassy crust forms around the newly extruded lava, forming an expanded pillow. Next, pressure builds until the crust breaks and new basalt extrudes like toothpaste, forming another pillow. Lava: Pillow

11 Pyroclastic Material: Blocks A volcanic block is a solid rock fragment greater than 64 mm in diameter that was ejected from a volcano during an explosive eruption.A volcanic block is a solid rock fragment greater than 64 mm in diameter that was ejected from a volcano during an explosive eruption.

12 Pyroclastic Material: Bombs Volcanic bombs are lava fragments that were ejected while viscous (partially molten) and larger than 64 mm in diameter. Many acquire rounded aerodynamic shapes during their travel through the air.Volcanic bombs are lava fragments that were ejected while viscous (partially molten) and larger than 64 mm in diameter. Many acquire rounded aerodynamic shapes during their travel through the air.

13 Pyroclastic Material: Lapilli Rock fragments between 2 and 64 mm ( in) in diameter that were ejected from a volcano during an explosive eruption are called Lapilli.Rock fragments between 2 and 64 mm ( in) in diameter that were ejected from a volcano during an explosive eruption are called Lapilli.

14 Pyroclastic Material: Ash Volcanic ash consists of rock, mineral, and volcanic glass fragments smaller than 2 mm (0.1 inch) in diameter, which is slightly larger than the size of a pinhead.Volcanic ash consists of rock, mineral, and volcanic glass fragments smaller than 2 mm (0.1 inch) in diameter, which is slightly larger than the size of a pinhead.


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