Science Test Chapter-9
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- what lava is so thick in consistency that it barely creeps along the ground?
- blocky lava
- in large scale eruptions volcanic ash along with sulfur rich gases can reach the upper atmosphere as the gases spread around the globe they can block sunlight causing what?
- the tempature to drop noticeably
- what are volcanoes that have not erupted in recorded history and probably never will again called?
- extinct volcanoes
- what forms when a magma chamber that supplies material to a volcano empties material and its roof collapses?
- caldera
- where is nearly 75 oercent of the worlds active volcanoes on land occur?
- ring of frie
- explosive eruptions are also caused by magma that contains a large percentage of what?
- silica
- where do most volcanoes occur ?
- tectonic plate boundaries
- the movement of one tectonic plate under another is called what?
- subduction
- why are most volcanoes on tectonic plate boundaries?
- these boundaries are where the plates either collide with one another or separate from one another
- non-explusivve eruptions that form rivers of red-hot lava?
- lava flows
- what are central vent in most volcanoes is a funnel shaped pit called what?
- crater
- what type of volcanoes are built out of layers of lava from repeated nonexplosive eruptions?
- shield volcanoes
- what are the two types of volcanic eruptions?
- explosive and non-explosive
- magma rises through holes in the Earth's crust called what?
- vents
- what consists of the rock fragments created by explosive volcanic eruptions?
- Pyroclastic Material
- these are large blobs of magma that harden in the air?
- volcanic bombs
- what makes a volcano more likely to erupt explosively if its high in this?
- water
- forms when the gases in stiff magma expand rapidly and the walls of the gas bubbles explode into tiny glasslike slivers?
- volcanic ash
- what is magma that flows onto the Earth's surface
- lava
- what are volcanoes that are not currently erupting but have erupted at some time in recorded history
- dormant volcanoes
- are small volcanic cones made entirely fo pyroclastic material from moderatly explisive eruptions?
- cinder cone volcanoes
- what begin deep in the earth possibly at the boundary between the mantlye and the core?
- mantle plumes
- what is a mountain that forms when molten rock called magma is forced to the Earth's surface?
- volcano
- these are pebble like bits of magma that became solid before they hit the ground?
- Lapilli
- what forms when lava erupts underwater?
- Pillow Lava
- what do scientists use to prudect eruptions?
- small bulges in the volcanoes slope may form as magma pushes against the inside of the volcano
- what are volcanoes that are in teh process of erupting or that show signs of eruting in the very near future?
- active volcano
- this lava flows slowly?
- Pahoehoe
- what are two tectonic plates collide occur where?
- convergent boundary
- sometimes referred to as stratovolcanoes are one of the most common types of volcanoes they from by explosive eruptions of pyroclastic material followed by quieter outpourings of lava?
- composite volcanoes
- what are tectonic plates that separate and move away from each other called?
- divergent boundary
- what is another way volcanoes can form?
- density
- these are the largest pieces of pyroclastic material?
- volcanic blocks
- this lava is slightly stiffer lava pours out quickly and forms a brittle crust?
- Aa
- what are places on the earths surface that are directly above comumns of rising magma ?
- hot spots
- as an increase in what raises the melting point of most materials ?
- pressure
- what are lond mountain chains underwater called?
- mid ocean ridges
- they attach this instrument called what to the surface of the volcano scientists can detect small changes in the angle of the slope?
- tiltmeter