Ensys 12 Cert.
UNIT: Natural Disasters
Mr. Muller
Ensy 12 – Unit: Natural Disasters – “Study Guide”
Volcanoes:
1. A volcano is a landform where molten rock erupts through the surface of the planet.
2. A volcano is a mountain that opens downward to a pool of molten rock below the surface of
the earth.
3. A volcano is a hole in the Earth from which molten rock and gas erupt.
4. The word Volcano is derived from the name of Vulcan, who was the god of fire in Roman
mythology.
5. Volcanic eruptions occur because the pressure of the molten rock builds up and needs to
escape.
6. “Fissures” are the narrow cracks in the earth’s crust through which the molten rock called
“Magma”, escapes to the surface of the Earth.
7. Once the magma reaches the earth’s surface it is referred to as “Lava”.
8. The Earth is made of three layers; the Crust, the Mantle and the Core.
9. The Earth’s crust is made up of huge slabs called plates. When two plates collide, one
section slides on top the other with the one beneath being pushed down, thus squeezing the
magma up between the two plates.
10. Volcanic eruptions may also trigger other natural disasters such as tsunamis, flash floods,
earthquakes, mud flows and rock falls.
11. The gases that are produced by the eruptions may kill people and animals as they are
poisonous.
12. Volcanic dust causes pneumonia and illnesses to the survivors and dark skies, severe winds
and heavy rains may follow an eruption for months afterwards.
13. People set up homes on the slopes of volcanoes because of the rich and fertile soil that is
produced.
14. There are three different types of Volcanoes; active, dormant and extinct.
15. There are four different shapes of volcanoes; these shapes are created from the type of
magma that exists in that area of the Earth.
16. “Shield volcanoes” are shaped like a bowl or shield in the middle with long gentle slopes
made by the lava flows.
Ensys 12 Cert.
UNIT: Natural Disasters
Mr. Muller
17. “Composite volcanoes” are steep-sided volcanoes composed of many layers of volcanic rock.
18. “Cinder Cone volcanoes” are circular or oval cones built from erupting lava that breaks into
small pieces as it shoots into the air.
19. “Lava Dome volcanoes” are formed when erupting lava is too thick to flow and makes a
steep-sided mound as the lava piles up.
20. The world’s largest active volcano is “Mauna Loa”, a shield volcano, which is located in
Hawaii, USA.
Ensys 12 Cert.
UNIT: Natural Disasters
Mr. Muller
Earthquakes:
1. An earthquake (also known as a quake, tremor or temblor) is the result of a sudden release
of energy in the Earth's crust that creates seismic waves.
2. Seismic activity refers to the frequency, type and size of earthquakes experienced over a
period of time.
3. Seismometers or Seismographs are instruments that measure motions of the ground,
including those of seismic waves generated by earthquakes, volcanic eruptions, and other
seismic sources.
4. Seismic waves are waves of energy that travel through the earth, and are a result of an
earthquake, explosion, or a volcano that imparts low-frequency acoustic energy.
5. An earthquake shakes the ground because of the movement of tectonic plates that are in
the outside layer of the earth.
6. Tectonic plates are pieces of the Earth's crust and uppermost mantle, together referred to as
the lithosphere.
Ensys 12 Cert.
UNIT: Natural Disasters
Mr. Muller
7. Convection currents beneath the plates move the plates in different directions.
8. The source of heat driving the convection currents is radioactive decay which is happening
deep in the Earth.
9. Underneath the Earth’s crust, the rock is so hot that it remains molten and flows like a
liquid.
10. The plates float on the molten layer and move very slowly, only few centimeters per year.
11. About 80 percent of all the planet's earthquakes occur along the rim of the Pacific Ocean,
called the "Ring of Fire".
12. The “Ring of Fire” is the home of the most active volcanoes in the world.
13. Around 132 AD, Chinese scientist Chang Heng invented the first seismoscope, an instrument
that could register the occurrence of an earthquake. Heng's invention was called the dragon
jar.
14. There are many types of earthquakes such as Tectonic, Volcanic and Collapse.
15. Tectonic earthquakes occur when rocks in the earth's crust break due to geological forces
created by movement of tectonic plates. Tectonic earthquakes are the most common type
of earthquake. This type does not have a specific magnitude; it may be of a small or of
extremely high magnitude.
16. Volcanic earthquakes are not as common as the tectonic. Volcanic earthquakes happen after
a volcanic activity and there are two types: Volcanic Tectonic earthquakes and Long Period
Volcanic earthquakes. Volcanic tectonic earthquakes usually occur after of a volcanic
eruption.
17. Collapse earthquakes usually do not have a large magnitude, and usually take place around
underground mines. Collapse earthquakes are also caused by seismic waves produced from
the explosion of rock on the earth’s surface.
18. The magnitude of most earthquakes is measured on the Richter scale, invented by Charles F.
Richter in 1934.
19. Another way to measure the strength of an earthquake is to use the Mercalli scale. Invented
by Giuseppe Mercalli in 1902, this scale uses the observations of the people who
experienced the earthquake to estimate its intensity.
20. A major difference between the earthquake intensity and magnitude lies in the fact that
magnitude of an earthquake is determined based on measuring the ground motion with
instruments (seismographs), whereas the intensity of an earthquake is determined based on
observations of earthquake effects on building structures and human perceptions.
Ensys 12 Cert.
UNIT: Natural Disasters
Mr. Muller
Tsunamis:
1. A Tsunami is a series of water waves caused by the displacement of a large volume of a body
of water, typically an ocean or a large lake.
2. A Tsunami is caused by unexpected movement on the ocean floor.
3. This unexpected movement can be caused by an earthquake, a powerful volcanic eruption,
or an underwater landslide.
4. The impact of a large meteorite may also cause a tsunami.
5. Tsunamis are sometimes referred to as tidal waves.
6. The principal generation mechanism (or cause) of a tsunami is the displacement of a
substantial volume of water or perturbation of the sea. This displacement of water is usually
attributed to earthquakes, landslides, volcanic eruptions, and glacier calving or more rarely
by meteorites and nuclear tests. The waves formed in this way are then sustained by gravity.
Tides do not play any part in the generation of tsunamis.
7. Tsunamis can be generated by seismicity when the sea floor abruptly deforms and vertically
displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that
are associated with the Earth's crustal deformation; when these earthquakes occur beneath
the sea, the water above the deformed area is displaced from its equilibrium position.
8. The Pacific Ocean is the prone to tsunamis as a result of huge geological undersea activity.
More specifically, when this happens, huge volumes of ocean water are pushed upward and
a wave is formed.
Ensys 12 Cert.
UNIT: Natural Disasters
Mr. Muller
9. Tsunamis have small amplitude (wave height) offshore, which is why they generally pass
unnoticed at sea. They grow in height when they reach shallower water, in a wave shoaling
process as seen in the diagram. A tsunami can occur in any tidal state and even at low tide
can still flood coastal areas.

When the wave enters shallow water, it slows down and its amplitude (height)
increases
10. In the 1950s, it was discovered that larger tsunamis than had previously been believed
possible could be generated by giant landslides. Underwater landslides that generate
tsunamis are called “Sciorrucks”.
11. Some meteorological conditions that cause tropical cyclones can generate a storm surge,
called a “Meteotsunami”, which can raise tides several meters above normal levels. As these
storm surges reach shore, they may resemble though are not tsunamis.
12. About 80% of tsunamis occur in the Pacific Ocean, but they are possible wherever there are
large bodies of water, including lakes.
13. If the first part of a tsunami to reach land is a trough—called a drawback—rather than a
wave crest, the water along the shoreline recedes dramatically, exposing normally
submerged areas.
14. As with earthquakes, several attempts have been made to set up scales of tsunami intensity
or magnitude to allow comparison between different events.
15. The first scales used routinely to measure the intensity of tsunami were the SiebergAmbraseys scale, used in the Mediterranean Sea and the Imamura-Iida intensity scale, used
in the Pacific Ocean.
16. The first scale that genuinely calculated a magnitude for a tsunami, rather than intensity at a
particular location was the ML scale proposed by Murty & Loomis based on the potential
energy.
17. Drawbacks can serve as a brief warning of tsunamis. People who observe drawback (many survivors
report an accompanying sucking sound), can survive only if they immediately run for high ground or
seek the upper floors of nearby buildings.
18. Regions with a high tsunami risk typically use tsunami warning systems to warn the population
before the wave reaches land. On the west coast of the United States, which is prone to Pacific
Ocean tsunami, warning signs indicate evacuation routes.
Ensys 12 Cert.
UNIT: Natural Disasters
Mr. Muller
Tornadoes:
1. A Tornado is a violently rotating column of air that is in contact with both the surface of the
earth and a cumulonimbus cloud.
2. Tornadoes are often referred to as twisters.
3. Tornadoes come in many shapes and sizes, but they are typically in the form of a visible
condensation funnel.
4. The narrow end touches the earth and is often encircled by a cloud of debris and dust.
5. Most tornadoes have wind speeds less than 110 miles per hour (177 km/h), are about 250
feet (76 m) across, and travel a few miles (several kilometers) before dissipating.
6. Various types of tornadoes include the landspout, multiple vortex tornado, and waterspout.
7. Waterspouts are characterized by a spiraling funnel-shaped wind current, connecting to a
large cumulus or cumulonimbus cloud. They develop over bodies of water.
8. Tornadoes have been observed on every continent except Antarctica. However, the vast
majority of tornadoes in the world occur in the Tornado Alley region of the United States.
9. Tornadoes can be detected before or as they occur through the use of Pulse-Doppler radar
by recognizing patterns in velocity and reflectivity data, such as hook echoes, as well as by
the efforts of storm spotters.
10. There are several scales for rating the strength of tornadoes. The Fujita scale (F) rates
tornadoes by damage caused and have been replaced in some countries by the updated
Enhanced Fujita Scale (EF). An F0 or EF0 tornado, the weakest category, damages trees, but
Ensys 12 Cert.
UNIT: Natural Disasters
Mr. Muller
not substantial structures. An F5 or EF5 tornado, the strongest category, rips buildings off
their foundations and can deform large skyscrapers.
11. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most
powerful known tornadoes.
12. The word tornado is an altered form of the Spanish word tronada, which means
"thunderstorm”.
13. Tornadoes occasionally accompany tropical storms and hurricanes that move over land.
Tornadoes may appear nearly transparent until dust and fragments are picked up.
Occasionally, two or more tornadoes may occur at the same time.
14. Tornadoes can have a wide range of colors, depending on the environment in which they
form. Those that form in dry environments can be nearly invisible, marked only by swirling
debris at the base of the funnel. Condensation funnels that pick up little or no debris can be
gray to white.
15. While traveling over a body of water (as a waterspout), tornadoes can turn very white or
even blue. Slow-moving funnels, which ingest a considerable amount of debris and dirt, are
usually darker, taking on the color of debris.
16. Tornadoes in the Great Plains can turn red because of the reddish tint of the soil, and
tornadoes in mountainous areas can travel over snow-covered ground, turning white.
17. A vortex, when we are taking about tornadoes is the centre of the tornado. This is where the rapid
movement of the air in the tornado is its strongest as there is the most force in this area. As the air
has less of a distance to travel to make a full rotation, the speed of the vortex is a lot stronger than
the outer areas of the tornado. TORNADO WARNING SIGN
18. A tornado warning (SAME code: TOR) is an alert issued by weather services to warn that
severe thunderstorms with tornadoes may be imminent. It can be issued after a tornado or
funnel cloud has been spotted by eye or more commonly if there are radar indications of
tornado formation.
19. Specific Area Message Encoding or “SAME” is the protocol used to encode the Emergency
Alert System (EAS) and NOAA Weather Radio's SAME Public Warning System in the U.S. and
Weatheradio Canada in Canada.