2. Natural Disasters
A natural disaster is the effect of a
natural hazard (e.g., flood, tornado,
hurricane, volcanic eruption,
earthquake, or landslide)
Disasters
Disasters are hazards that cause destruction or
environmental changes.
The types are
Natural disasters
3. List of top 10 natural disasters
1. Cyclone
2. Earthquake
3. Tornado
4. Volcanic Eruption
5. Tsunami
6. Flood
7. Landslide
8. Drought
9. Waterspout
10. Wildfire
4. Cyclones
• A cyclone is an area of closed, circular fluid motion. It
has low pressure on the inside and high pressure on
the outside.
• The center of the storm is called the eye and it has the
calmest water and the lowest pressure
• Cyclones turn counter-clockwise in the northern
hemisphere and clockwise in the southern hemisphere.
This is because it follows the rotational movemeent of
the earth.
• The biggest cyclone recorded is the Bhola cyclone. It
hit the coast of today's Bangladesh in 1970 with a
death toll of around 500,000.
5. Earthquakes
.
• An earthquake (also known as a quake, tremor or temblor) is the
perceptible shaking of the surface of the Earth, which can be violent
enough to destroy major buildings and kill thousands of people.
• The severity of the shaking can range from barely felt to violent
enough to toss people around.
• Earthquakes have destroyed whole cities. They result from the
sudden release of energy in the Earth's crust that creates seismic
waves.
• The seismicity, seismism or seismic activity of an area refers to the
frequency, type and size of earthquakes experienced over a period
of time.
• The power of an earthquake is measured by Richter scale
6. Tornados (Twisters)
• A tornado is a violently rotating column of air that is in contact with both the
surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a
cumulus cloud.
• They are often referred to as twisters or cyclones, although the word cyclone is
used in meteorology, in a wider sense, to name any closed low
pressure circulation.
• Tornadoes come in many shapes and sizes, but they are typically in the form of a
visible condensation funnel, whose narrow end touches the earth and is often
encircled by a cloud of debris and dust.
• Most tornadoes have wind speeds less than 110 miles per hour (180 km/h), are
about 250 feet (80 m) across, and travel a few miles (several kilometers) before
dissipating.
• The most extreme tornadoes can attain wind speeds of more than 300 miles per
hour (480 km/h), stretch more than two miles (3 km) across, and stay on the
ground for dozens of miles (more than 100 km).
7. Volcanic Eruption
• Several types of volcanic eruptions—wherein lava , tephra (ash , lapilli
, volcanic bombs and blocks), and assorted gases are expelled from
a volcanic vent or fissure—have been distinguished by volcanologists.
• Some volcanoes may exhibit only one characteristic type of eruption
during a period of activity, while others may display an entire sequence of
types all in one eruptive series.
• There are three different meta types of eruptions. The most well-
observed are magmatic eruptions, which involve the decompression of gas
within magma that propels it forward.
• Preheat o magmatic eruptions are another type of volcanic eruption,
driven by the compression of gas within magma, the direct opposite of the
process powering magmatic activity.
• The last eruptive metatype is the prehatic eruption, which is driven by
the superheating of steam via contact with magma; these eruptive types
often exhibit no magmatic release, instead causing the granulation of
existing rock.
8. Tsunami’s
• A tsunami called the "harbour wave" also known as a seismic sea wave or as
a tidal wave, is a series of waves in a water body caused by the displacement of a
large volume of water, generally in an ocean or a large lake.
• Earthquakes , volcanic eruptions and other underderwater explosions ,
landslides, meteorite impacts and other disturbances above or below water all
have the potential to generate a tsunami.
• Tsunami waves do not resemble normal sea waves, because their wavelength is far
longer. Rather than appearing as a breaking wave, a tsunami may instead initially
resemble a rapidly rising tide, and for this reason they are often referred to as tidal
waves.
• Tsunamis generally consist of a series of waves with periods ranging from minutes
to hours, arriving in a so-called "wave train". Wave heights of tens of metrs can be
generated by large events.
• Although the impact of tsunamis is limited to coastal areas, their destructive
power can be enormous and they can affect entire ocean basins
• the 2004 Indian Ocean tsunami was among the deadliest natural disasters in
human history with at least 230,000 people killed or missing in 14 countries
bordering the Indian Ocean.
9. Landslides
• A landslide or a landslip is a movement in the ground and a shallow flow
of debris.
• The largest landslide in history happened because of Mount St. Helens.
3km of rock moved downhill.
• A landslide, also known as a landslip, is a geological phenomenon that
includes a wide range of ground movements . Rockfalls , deep failure
of slopes and shallow debris flows were common.
• Landslides can occur in offshore, coastal and onshore environments.
Although the action of gravity is the primary driving force for a landslide to
occur, there are other contributing factors affecting the original slope
stability.
• Typically, pre-conditional factors build up specific sub-surface conditions
that make the area/slope prone to failure, whereas the actual landslide
often requires a trigger before being released.
•
10. Floods
• .
• Flooding may occur as an overflow of water from water bodies,
such as a river or lake, in which the water overtops or breaks levees,
resulting in some of that water escaping its usual boundaries, or it
may occur due to an accumulation of rainwater on saturated
ground in an areal flood.
• Floods can also occur in rivers when the flow rate exceeds the
capacity of the river channel, particularly at bends or meanders in
the waterway. Floods often cause damage to homes and businesses
if they are in the natural flood plains of rivers.
• One of the biggest floods in the world is probably the Yellow river
in China 1887 which killed between around 900,000
11. Droughts
• Drought is an extended time when a region receives a deficiency in its water
supply , whether atmospheric, surface or ground water . A drought can last for
months or years, or may be declared after as few as 15 days
• . Generally, this occurs when a region receives consistently below
average precipitation. It can have a substantial impact on the ecosystem and
agriculture of the affected region.
• Annual dry seasons in the tropics significantly increase the chances of a drought
developing and subsequent bush fires. Periods of heat can significantly worsen
drought conditions by hastening evaporation of water vapor.
• Many plant species, such as those in the family . Cacti, have adaptations like
reduced leaf area and waxy cuticles to enhance their ability to tolerate drought.
Some others survive dry periods as buried seeds.
• Lasting three years from 1958 to 1961, the Great Chinese Famine is the worst on
record, 15 to 43 million were killed as a result
• .
12. Water spouts
• A waterspout is an intense columnar vortex (usually appearing as
a funnel-shaped cloud) that occurs over a body of water. They are
connected to a towering cumuliform cloud or a cumulonimbus cloud. In
the common form, it is a non-super cell tornado over water.
• Most waterspouts do not suck up water; they are small and weak rotating
columns of air over water.
• While waterspouts form mostly in the tropics and subtropical areas, other
areas also report waterspouts, including Europe, New Zealand, the Great
Lakes and Antarctica. Although rare, waterspouts have been observed in
connection with lake-effect snow precipitation bands.
• Waterspouts have a five-part life cycle: formation of a dark spot on the
water surface, spiral pattern on the water surface, formation of a spray
ring, development of the visible condensation funnel, and ultimately
decay.
13. Wildfire
• A wildfire is an uncontrolled fire in an area of combustible
vegetation that occurs in the countryside area.
• / a wildfire differs from other fires by its extensive size, the
speed at which it can spread out from its original source, its
potential to change direction unexpectedly, and its ability
to jump gaps such as roads, rivers and fire breaks.
• Wildfires are characterized in terms of the cause of
ignition, their physical properties such as speed
of propagation , the combustible material present, and the
effect of weather on the fire.
• Other names for a wildfire are brush fire, bushfire, forest
fire, desert fire, grass fire, hill fire, peat fire, vegetation fire,
and veldfire.
