Earthquake fault types

An earthquake is a massive release in energy from the movement of the tectonic plates which make up the earth’s crust.

Areas of the earth’s surface where tectonic plates meet are known as faults, the tectonic plates slide past each other, but sometimes they become stuck and this causes energy to be stored, as the energy builds the plates will eventually become unstuck causing them to jolt quickly, releasing the stored up energy over a short period of time, this energy radiates outwards as what we call seismic waves. The more energy that was stored before the sudden release, the stronger the seismic waves.

Earthquakes are very difficult to predict but sometimes there are smaller shocks, called foreshocks which happen just before the mainshock, which can warn people to take precautions. Sometimes after the mainshock there can be powerful aftershocks which can happen any time after the earthquake, these are usually less powerful but can still be damaging.

The majority of the time earthquakes occur at fault lines and they’re less likely to happen elsewhere. This is why earthquakes are far more frequent in certain countries, because these countries are sitting on one or sometimes multiple fault lines.

How do we measure the strength of earthquakes?

The majority of earthquakes are too minor have an effect on people but sometimes they can be very destructive, the tremors being violent enough to destroy buildings or even entire cities. The magnitude of an earthquake is measured with a seismometer and the level is recorded on the Richter scale. The Richter scale is logarithmic, which means every point on the scale is ten times stronger than the last, so for example, an earthquake measured to be at 5.0 on the Richter scale is 10 times stronger than one measured to be at 4.0, which would make a 7.0 1000 times stronger than a 4.0 earthquake.

There are roughly 10,000 earthquakes a day around the world or around 3 million per year. The majority of these earthquakes measure at less than 3.0 on the Richter scale so they’re no felt by people. But occasionally earthquakes can be much stronger.

Earthquakes in History

While most earthquakes go unnoticed, sometimes they can be so strong they cause devastation.

The strongest earthquake ever to have been recorded was in Valdivia, Chile rated at 9.5 in magnitude. Nearly half the houses in in Valdivia were destroyed leaving around 20,000 people homeless and the resulting tsunami affected many other countries. It’s estimated that up to 6,000 people may have died as a result of the earthquake.

Destroyed houses in Chile

More recently was the 2004 earthquake in the Indian Ocean, this earthquake had a lower magnitude of roughly 9.0 but caused a tsunami so large it devastated many countries coastlines (particularly Indonesia, Sri Lanka, India and Thailand) and was one of the deadliest earthquakes in history.

Planets

Our solar system consists of the Sun and anything that orbits it. Eight planets orbit the sun and ordered from closest to furthest away they are named Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. No planet other than Earth has been found to contain any living organisms.

In addition to these eight planets there are five “dwarf planets” which are just like planets, only they are of lower mass. These are, Ceres, Pluto, Haumea, Makemake and Eris. Pluto was considered a planet up until 2006 when scientists reclassified it as a dwarf planet.

Six of the eight planets have moons, or “natural satellites”. They are divided into two groups, the four planets closer to the Sun are known as “Inner Planets” and the other four as “Outer Planets”

The four inner planets don’t have rings around them, are solid and dense and either have only one moon or none at all. Of these four planets, three of them (Earth, Venus and Mars) have atmospheres that are strong enough to generate weather. The outer planets are much more massive than the inner, it is thought that they make up roughly 99% of the mass to orbit our Sun. Jupiter and Saturn are much larger than the Earth and are made up of Hydrogen and Helium – Uranus and Neptune are much smaller than Earth, but all four are known as “gas giants”. All four of the gas giant have rings of dust or debris surrounding them, but Saturn’s is much more substantial the other’s and can be seen from Earth.

The Sun

Sun With Solar Flare

The Sun is our solar system’s only star. It is roughly 333,000 times the mass of the Earth but it’s diameter is only 109 times larger and is just under 150 million kilometers away from Earth. It is roughly 75% hydrogen and most of the rest is helium. The Sun is 4.57 billion years old, approximately halfway through the time it will spend as a main sequence star, in another 5 billion years, the Earth will become a red giant and then  as it cools will become what is known as a white dwarf.

The Sun provides the earth with sunlight, which is vital for life.

A Typical Composite Volcano

Volcanoes are ruptures in the planet’s surface which allow magma, volcanic ash and gasses to escape from beneath the earth’s crust. They are commonly found where tectonic plates diverge or converge.

Diverging tectonic plates are moving away from each other, and converging plates are those that are moving towards each other.

Most land volcanoes are caused by converging tectonic plates, one of the plates forces the other one downwards into the earth’s mantle, which is very hot, this high temperature causes an increase in pressure which causes the rocks which form the tectonic plate to melt and form a magma reservoir shown in the image . When this magma reservoir’s pressure builds enough to break through the earth’s crust, this causes a volcanic eruption.

Volcanic eruptions can be very destructive, not only can they cause a lot of damage to areas near the volcano, but they can fill the sky with volcanic ash which can be a threat to aircraft. Volcanoes can also cause volcanic winters where volcanic ash and sulphuric acid can cause the earth’s temperature to drop, which can cause the death of both people and any other forms of life on a large scale.

History

In recorded history, around 650 volcanoes have erupted while in an average year around 60 are active and there are around 20 erupting at any given time. There have probably been millions of volcanoes in the earth’s history and it’s more likely most of them have been at the bottom of the sea rather than on land. This is because most areas with diverging tectonic plates are located in the sea.

The picture above shows a “conical” volcano, gasses and and molten lava coming from a crater at the top, which is the what most people usually picture when they think of volcanoes. This is only one of many types, however and most do not look like this. They can take many forms. Below are some pictures of recently erupted volcanoes.

Fourpeaks in Alaska

Mount Kea in Hawaii

5 interesting facts!

• The tallest known volcano is on Mars and is called “Olympus Mons”. It measures at roughly 27km tall, which is over 6 times taller than the tallest volcano on earth which is Mouna Kea (pictured above).

• If a volcano ejects more than 1000 cubic meters, it is known as a “super volcano”. Most historic eruptions are roughly 1/1000th the size of these.

• As well as on the ocean floor, sometimes volcanoes can form under icecaps, there are plenty of these to be found in iceland.

• Over 75% of the earth’s volcanoes can be found in the pacific ring of fire, an area around the pacific ocean. This is due to it being a large area of converging tectonic plates.

• The hot liquid rock beneath the earth’s surface is known as magma, however as soon as it leaves the volcano, it is then known as lava.