How and the different types of disasters that are found in the universe we live in.

1. Natural Disasters
By Andrei Farrugia 3.1

2. Summary
• A natural disaster is the effect of a natural hazard like a flood, hurricane, volcanic
eruption, earthquake and heat wave.
• This leads to financial, environmental or human losses. The resulting loss depends
on the tecknology of the population and if they know how to prevent the hazard,
also called their resilience.
• If these disasters were to continue they would be a great danger to the earth.
• A natural hazard will not result into a natural disaster in areas without vulnerability
like strong earthquakes in inhabited areas.
• Natural disasters occur in very different ways and forms and there are many reasons
why they occur.
• Most of them are natural and some of them are cause due to the damage that the
human race is doing to the earth.

3. Avalanche
• An avalanche also known as a snowslide or snowslip is a sudden, drastic
flow of snow down a slope. This occurs when either natural triggers such
as weight from snow or rain and earthquakes or artificial triggers such as
snowmobilers, explosives or backcountry skiers that overload the snowpack.
• The influence of gravity on the accumulated weight of newly fallen uncompacted
snow or on thawing older snow leads to avalanches which may be triggered by
earthquakes, gunshots and the movements of animals.
• Avalanches are most common during winter or spring but glacier movements may
cause ice avalanches during summer.
• In contrast to other natural events which can cause disasters, avalanches are not rare
or random events and are endemic to any mountain range that accumulates a
standing snowpack.

4. Earthquakes
• 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.
• The seismic activity of an area refers to the frequency, type and size of
earthquakes experienced over a period of time.
• Earthquakes are measured using observations from seismometers. The moment
magnitude is the most common scale on which earthquakes larger than
approximately 5 are reported for the entire globe.
• The more numerous earthquakes smaller than magnitude 5 reported by national
seismological observatories are measured mostly on the local magnitude scale, also
referred to as the Richter scale.
• At the Earth's surface, earthquakes manifest themselves by shaking and sometimes
displacement of the ground. When the epicenter of a large earthquake is located
offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes
can also trigger landslides, and occasionally volcanic activity.

5. Volcanic Eruptions
• During a volcanic eruption, lava and various gases are expelled from a volcanic
vent or fissure. Several types of volcanic eruptions have been distinguished
by volcanologists.
• There are three different metatypes of eruptions. The most well-observed
are magmatic eruptions, which involve the decompression of gas within magma that
propels it forward.
• Volcanic eruptions arise through three main mechanisms: Gas release under
decompression causing magmatic eruptions, Thermal contraction from chilling on
contact with water causing phreatomagmatic eruptions and Ejection of entrained
particles during steam eruptions causing phreatic eruptions.
• There are two types of eruptions in terms of activity, explosive eruptions and effusive
eruptions. Explosive eruptions are characterized by gas-driven explosions that
propels magma and tephra. Effusive eruptions, meanwhile, are characterized by the
outpouring of lava without significant explosive eruption.

6. Floods
• A flood is an overflow of an expanse of water that fills land with water. Flooding may
result from the volume of water within a body of water, such as a river or lake, which
overflows or breaks levees, with the result that some of the water escapes its usual
boundaries.
• While the size of a lake or other body of water will vary with seasonal changes in
precipitation and snow melt, it is not a significant flood unless such escapes of water
endanger land areas used by man like a village, city or other inhabited area.
• Floods can also occur in rivers, when the water flow exceeds the capacity of the river
channel, particularly at bends. Floods often cause damage to homes and businesses if
they are placed in natural flood plains of rivers.
• While flood damage can be virtually eliminated by moving away from rivers
and other bodies of water, since time out of mind, people have lived and
worked by the water to seek sustenance and capitalize on the gains of
cheap and easy travel and commerce by being near water.

7. Drought
• A drought is an extended period of months or years when a region notes a deficiency
in its water supply whether surface or underground water. Generally, this occurs
when a region receives consistently low average of water by precipitation.
• This global phenomenon has a widespread impact on agriculture. The United
Nations estimates that an area of fertile soil the size of Ukraine is lost every year
because of drought, deforestation, and climate instability.
• Periods of drought can have significant environmental, agricultural, health, economic
and social consequences. The effect varies according to vulnerability. For example,
farmers are more likely to migrate during drought because they do not have
alternative food sources. Areas with populations that depend on as a major food
source are more vulnerable to drought-triggered famine.
• Drought is a normal, recurring feature of the climate in most parts of the world. It is
among the earliest documented climatic events, present in the Epic of Gilgamesh and
tied to the biblical story of Joseph's arrival in and the later Exodus from Ancient
Egypt.

8. Tornadoes
• A tornado is a violent, dangerous, 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 a twister or a cyclone. Tornadoes
come in many shapes and sizes, but 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 (177 km/h), are
approximately 250 feet (76 m) across, and travel a few miles (several kilometers)
before dissipating. The most extreme tornadoes can attain wind speeds of more than
300 mph (480 km/h), stretch more than two miles (3.2 km) across, and stay on the
ground for dozens of miles (more than 100 km).
• 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, although they can occur nearly anywhere
in North America.

9. Heat Waves
• A heat wave is a prolonged period of excessively hot weather, which may be
accompanied by high humidity. There is no universal definition of a heat wave; the
term is relative to the usual weather in the area. Temperatures that people from a
hotter climate consider normal can be termed a heat wave in a cooler area if they are
outside the normal climate pattern for that area. The term is applied both to routine
weather variations and to extraordinary spells of heat which may occur only once a
century. Severe heat waves have caused catastrophic crop failures, thousands of
deaths from hypothermia, and widespread power outages due to increased use of air
conditioning.
• They occur in the summer in warm climates, in an area of high pressure with little or
no rain or clouds and when the air and ground easily heats much more than it’s
supposed to. A static high pressure area can impose a very persistent heat wave.
• Hypothermia, also known as heat stroke, becomes active during periods of sustained
high temperature and humidity. Sweating is absent from 84%–100% of those
affected. Older adults, very young children and those who are sick or overweight are
at a higher risk for heat-related illness.

10. Blizzards
• A blizzard is a severe snowstorm made by strong winds. By definition, the
difference between blizzard and a snowstorm is the strength of the wind.
To be a blizzard, a snow storm must have sustained winds or frequent
gusts that are greater than or equal to 56 km/h (35 mph) with blowing or
drifting snow which reduces visibility to 400 meters or ¼ mile or less and
must last for a prolonged period of time — typically three hours or more.
• Blizzards can bring near-whiteout conditions, and can paralyze regions for days at a
time, particularly where snowfall is unusual or rare. The 1972 Iran blizzard, which
caused approximately 4,000 deaths, was the deadliest in recorded history.
• Ground blizzards require high winds to stir up already fallen snow.

11. Impact Event
• An impact event is the collision of a large meteorite, asteroid, comet, or
other celestial object with the Earth or another planet. Throughout recorded history,
hundreds of minor impact events have been reported, with some occurrences causing
deaths, injuries, property damage or other significant localised consequences.
Impact events have been a plot and background element in science fiction since
knowledge of real impacts became established in the scientific mainstream.
• Earth has gone through periods of abrupt and catastrophic change, some due to the
impact of large asteroids and comets on the planet. A few of these impacts may have
caused massive climate change and the extinction of large numbers of plant and
animal species.
• The Moon is widely attributed to a huge impact early in Earth's history. Impact events
earlier in the history of Earth have been credited with creative as well as destructive
events; it has been proposed that impacting comets delivered the Earth's water, and
some have suggested that the origins of life may have been influenced by impacting
objects by bringing organic chemicals or life forms to the Earth's surface, a theory
known as exogenesis.

12. Tropical Cyclone
• A tropical cyclone is a storm system characterized by a low-pressure centre and
numerous thunderstorms that produce strong winds and heavy rain.
Tropical cyclones strengthen when water evaporated from the ocean is released as
the saturated air rises, resulting in condensation of water vapour contained in the
moist air. They are fueled by a different heat mechanism than other cyclonic
windstorms such as nor'easters ,European windstorms, and polar lows. The
characteristic that separates tropical cyclones from other cyclonic systems is that at
any height in the atmosphere, the centre of a tropical cyclone will be warmer than its
surroundings; a phenomenon called "warm core" storm systems.
• While tropical cyclones can produce extremely powerful winds and torrential rain,
they are also able to produce high waves and damaging storm surge as well as
spawning tornadoes. They develop over large bodies of warm water, and lose their
strength if they move over land due to increased surface friction and loss of the warm
ocean as an energy source.

13. Wildfire
• A wildfire is any uncontrolled fire in combustible vegetation that occurs in the
countryside or a wilderness area. Other names such as brush fire, bushfire, forest
fire, desert fire, grass fire, hill fire, peat fire, vegetation fire, and veldfire may be used
to describe the same phenomenon depending on the type of vegetation being
burned. 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.

14. Famine
• A famine is a widespread scarcity of food, caused by several factors
including crop failure, overpopulation, or government policies. This
phenomenon is usually accompanied or followed by
regional malnutrition, starvation, epidemic, and increased mortality. Every
continent in the world has experienced a period of famine throughout
history. Many countries continue to have extreme cases of famine.
Emergency measures in relieving famine primarily include providing
deficient micronutrients, such as vitamins and mineral,
through fortified sachet powders or directly
through supplements. The famine relief model increasingly used by aid
groups calls for giving cash or cash vouchers to the hungry to pay
local farmers instead of buying food from donor countries, often required
by law, as it wastes money on transport costs, but more importantly, it
perpetuates the cycle of dependency on foreign imports rather than helping
to create real local stability through agricultural abundance. Such
independence however does rest upon local conditions of soil, water,
temperature and so on.

15. Solar Flare
• A solar flare is a sudden brightening observed over the Sun surface or the solar
limb, which is interpreted as a large energy release of up to 6 ×
1025 joules of energy or 160,000,000,000 Megatons of TNT equivalent, over 25,000
times more energy released from the impact of Comet Shoemaker Levy-9 with
Jupiter. The flare ejects clouds of electrons, ions, and atoms through the corona into
space. These clouds typically reach Earth a day or two after the event. The term is
also used to refer to similar phenomena in other stars, where the term stellar
flare applies.
• Flares occur when accelerated charged particles, mainly electrons, interact
with the plasma. Scientific research has shown that the phenomenon
of magnetic reconnection is responsible for the acceleration of the charged
particles. On the Sun, magnetic reconnection may happen on solar
arcades – a series of closely occurring loops of magnetic lines of force.
These lines of force quickly reconnect into a low arcade of loops leaving a
helix of magnetic field unconnected to the rest of the arcade.