Science- Chapter 18-20 Study Guide
Which type lava-basaltic or rhyolitic lava-flows faster?Explain
Basaltic lava flows faster because lava continues less silica.
When magma reaches Earth's surface, it is called
lava.
What three factors affect the formation of magma?
Temperature, Pressure and Water
Rock fragments thrown into air during a volcanic eruption are called
tephra .
Forms when tephra are ejected into air then fall back to Earth and pile around a vent.
Cinder Cone
Magma that fuels this type of volcano contains large volumes of gases but not silica and water.
Cinder Cone
Small volcano with steep sides.
Cinder Cone
Forms from lava that us higher in water and silica content than lava that from shield volcanoes.
Cinder Cone, Composite
Forms when layers of tephra alternate with lava.
Composite
Fueled by magma that contains large amounts of silica, water, and gases
Composite
Mount St. Helens and Mount Rainier are examples
Composite
Potentially the most dangerous to humans and most destructive to the environemt
Composite
Does cooler magma flow more less quickly than hotter magma?
Cooler magma flows less quickly as viscosity increases.
Why isn't Earth's entire mantle liquid?
Even though temperature are high enough to melt rock the great pressure increases the melting temperature of the rocks most of the rock in the mantle do not melt.
Pressure decreases with depth below Earth's Surface
False
Pluton
Intrusive igneous rock body
Stock
Irregular shaped pluton that is similar to a batholith, but smaller in size.
Batholith
Largest pluton
Is the viscosity of magma that is high in silica higher or lower than magma that is low in silica?
Magma that is high silica has a higher viscosity than a magma low in silica.
Laccolith
Mushroom-shaped pluton.
Dike
Pluton that cuts across preexisting rocks.
Sill
Pluton that is parallel to the rocks it intrudes.
Mountain-Building
Process responsible for the formation of many plutons.
Forms from lava that contains relatively small amounts of gases and silica.
Shield Volcano
Forms when layers of basaltic lava accumulate during a nonexplosive eruption
Shield Volcano
Has broad, gently sloping sides and a nearly circular base.
Shield Volcano
Mauna Kea in Hawaii is an example.
Shield Volcano
As pressure increases, the temperature at which a dry substance melts increases.
True
Magma forms when rocks begin to melt.
True
Magma is a mixture of molten rock,suspended minerals, and gases.
True
Wet minerals and rock melt at lower temperatures than do dry minerals and rocks.
True
How does the viscosity of magma change as magma cools?
Viscosity increases with a decrease in temperature.
How is water present in rocks and minerals?
Water can either be held withing pore spaces within a rock or bound directly into a mineral structure. Clay minerals often times hold large amounts of water.
Which of the following forms when the top or side of a volcano collapses into the magma chamber?
caldera
A bowl-shaped depression that forms around the vent of a volcano is a
crater
The smallest tephra are
dust
Fast-moving clouds of gas,ash, and other tephra are
pyroclastic flows
Lava erupts through an opening in Earth's crust called a
vent
Large, angular volcanic fragments are called
volcanic blocks.
Large, rounded or streamlined tephra are called
volcanic bombs.
