Download Volcano

Science----Chapter 4 lesson 2- Earthquakes and Volcanoes
Test Friday, December 9, 2016
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Volcano-an opening in Earth’s crust through which lava may flow.
Focus- the point where an earthquake starts.
Lava- hot, melted rock that reaches Earth’s surface.
Hot spot- a stationary location in Earth’s mantle where magma
melts through a tectonic plate.
5. Epicenter- the point on Earth’s surface directly above the focus of
an earthquake.
6. Earthquake- a sudden shaking of Earth’s crust
Notes
1. Scientists can predict whether a volcano will erupt because the
volcano may give off smoke or steam, or there may be
earthquakes just before an eruption.
2. Walls and buildings may crumble during an earthquake because of
the ground trembling.
3. In this lesson, we learned that the shifting of a tectonic plate or
plates might make the ground move.
4. Earthquake waves travel through the layers of Earth.
5. Two scales used to measure earthquakes are the Richter scale and
the Mercalli scale.
6. The Richter scale measures magnitude at the epicenter. It rates
earthquakes from weakest to strongest, starting from 1.
7. The Mercalli scale is based on observed effects, not on
mathematics. The Mercalli scale rates earthquakes in Roman
numerals from 1 to XII, XII being the most severe.
8. The Mercalli scale is less reliable than the Richter scale.
9. When a volcano forms underwater as soon as the lava emerges
from the vent, the lava is cooled by the water and forms rock.
10 .If an underwater volcano kept erupting again and again the
mound of lava would grow taller and taller.
Three stages of volcanoes
1. Active volcanoes are currently erupting or have recently erupted.
2. Dormant volcanoes are volcanoes that have not erupted for some
time.
3. Extinct or dead volcanoes have stopped erupting.
Three ways volcanoes are formed
1. Shield volcanoes are built by thinner, fluid lava that spreads over
a large area. These mountains have a broad base and gently
sloping sides.
2. Cinder cone volcanoes are built by thick lava that is thrown high
into the air and falls as chucks or cinders. These mountains form
as a cone shape with a narrow base and steep sides.
3. Composite volcanoes are built by layers of ash and cinders
sandwiched between layers of hardened lava. The shape on one
side of a cone formed by a composite volcano usually looks the
same as the shape on the opposite side.