Machu Picchu

Not only is Machu Picchu one of the most important archaeological sites in South America, filled with historical mysteries, but it also boasts stunning views from the Peruvian Andes mountain range, 2,450 meters above sea level. Machu Picchu, in one of the Peruvian dialects, stands for Old Mountain and that is the name of the peak where the city is located.

Similar to most tropical locations, the season in Machu Picchu is divided into a rainy season which starts at October and ends on April the next year, and a dry season for the remainder of the year.

At the valley below the Incan city snakes the Urubamba River whose meandering path through the centuries carved cliffs some as high as 450 meters. The menacing cliffs plus the extreme elevation of the city made it a secret to the Spanish conquistadores who were searching in vain for the gold treasures of the fabled city of El Dorado. It was only through an Inca rope bridge at the Pongo de Mainique where a secret entrance to Machu Picchu for the exclusive use of the Inca army was found. Another bridge was found in a narrow gap between the river gorge.

It was formed by a felled tree trunk but the bridge could be easily set aside to discourage invaders. The tree trunk bridge was the only other access across the cliff whose sides drop almost 570 meters down into the river below.

The ancient city is situated in a saddle between two mountains important to Inca culture. While the other mountain was already named Machu Picchu, Huayna Picchu, which stands for Young mountain, is the other peak that nestles the ancient monument. Machu Picchu was by all means a self contained city.

It had a reliable water supply thanks to the ice fed rivers that flow along the Andes and enough level land for agriculture. Terraced hillsides added to the total amount of arable land and at same time made the slopes harder to ascend if ever invaders chose that path. Machu Picchu was a veritable fortress with easily defensible entrances. One entrance was the Sun Gate which traverses the mountains and leads to Cusco, the other was the Inca bridge.

 

Machu Picchu

 

 

View from the Incan city

Earthquakes

There are 3 main types of plate boundaries, all of which can cause earthquakes. These are destructive, constructive and conservative margins.

Destructive Boundary

- Subduction zones are one type of destructive boundary. This is where an oceanic and continental plate move together. The oceanic crust is more dense and therefore is submerged below the continental crust. Earthquakes occur where the plates rub together, bend and fracture. The oceanic crust melts, forming magma, which rises and forms a volcano. This occurs in the Andes.

  

- Collision zones are the other type of destructive boundary. This involves two continental plates moving towards each other. Earthquakes occur as rock folds and fractures. An example of this is in the Himalayas.

Constructive Boundary

This is where two oceanic plates are moving away from each other. The mantle near the gap that is made melts due to decreasing pressure. The mantle comes out as pillow lava when underwater, with volcanoes all the way down the ridge. There are minor earthquakes due to lava solidifying and collapsing. An example is the Mid Atlantic Ridge.

Conservative Boundary

Two plates rub against each others side as they move in opposite directions. The earthquakes caused by this can be extremely dangerous as often, the tension between the two plates builds up, before suddenly being released, causing dramatic shocks through the ground. The San Andreas Fault is an example of this.

The Atherton Tablelands

Inland of Cairns in Queensland, Australia. Home to some of the most beautiful waterfalls in the world. Millaa Millaa Falls being the most popular, and also where many adverts have been filmed, including L'oreal. The water drops 18.3 metres before plunging into a pool suitable for swimming.

Millaa Millaa Falls

Josephine Falls is well known for it's natural rock waterside.

Waterfalls are formed when a band of resistant rock lies next to less resistant rock. In this case, volcanic basalt rock. As the river flows over the rocks, the less resistant rock erodes faster, leaving resistant rock elevated above the stream below. This continues to occur  and a vertical drop is made. The erosion gradually undercuts the hard rock and eventually the resistant rock is unsupported and collapses. As the process continues, the waterfall retreats upstream. This can also cause a gorge to form. Abrasion and hydraulic action cause a plunge pool to form below the vertical drop. When the resistant rock collapses and falls into th  plunge pool, it contributes to abrasion as the loose rocks are swirled around and thrown at the sides of the pool, enlarging it further.

Whitehaven beach, Australia

Whitehaven beach is just one of many beaches in the the group of Whitsunday islands on the east coast of Australia. It is well known for it's fine, white, silica sand. The quartz-rich sand did not come from a local course as the rocks in the area do not contain large quantities of quartz. The sand drifted north along the Queensland coast, carried by prevailing sea currents and long shore drift, millions of years ago. Trapped by rocks and headbands, some sand accumulated to form the dunes of whitehaven beach. Over the years, sea levels rose and fell due to previous ice ages, causing impurities from the sand to be removed, leaving the sand fine and brilliantly white. The beach is also known as the shifting sands as each day the sand has been moved and displaced by the sea, so the beach looks different every day.

                            

     

 Whitehaven beach

Formation of the Himalyas

The Himalayan mountains are known to be young fold mountains. This is because they were formed relatively recently in earth's history compared to other mountain ranges, in a series of parallel ridges or folds extending for 2500km.

The theory behind the formation of these mountains is to do with plate tectonics and Continental Drift. On these plates lie the continents and oceans of the earth. Over 250 million years ago the continents formed a single mass called Pangea. The plates are constantly moving position due to mantle convection, gravity and the earth's rotation. This caused the land mass to gradually break apart, and then eventually collide with each other again. The Indian and Eurasian plates were squeezed together, building up pressure and stress, causing the crust to bend, fold or crumple. This created the Himalayas as the plates pushed up the rock between them. It take millions of years for mountains to be formed, and to this day the Himalayas are still rising but at a slower rate of about 5mm per year

The Himalayas

Pangaea

The Northern Lights

The northern lights or otherwise known as the aurora borealis, is a multi-coloured brilliant light show that can paint the sky with surreal colour.

The creation of the lights start with the sun and the activity it produces. The sun is constantly throwing particles out into space. These particles, often referred to as solar wind, is thrown toward the earth. This wind produced by the sun is a super hot stream of plasma made up of electrons and protons. As the violent wind approaches the earth, much of it is shielded off by the protection cover of the earth's magnetic field. As it hits the earth, the magnetic field guides the plasma towards the northern and southern poles where the particles can enter. As the solar particles enter the earth's atmosphere, they slam into the gas particles in the air. As they collide with each other, they create a glowing effect of different colours. As these lights are created by the solar wind thrown from the sun, they create oval rings around the northern magnetic pole.

In addition to the lights being various colours, they also appear to flow, form different shapes and dance in the sky. This is because the collisions between the atoms and the charged particles are constantly shifting along the magnetic currents of the earth's atmosphere and the reactions of these collisions follow the current.

Today scientists can predict the northern lights which can be shown in a similar way to a weather forecast. Winter is usually the best time to view them because there a re long periods of clear nights. One of the best places to view them is Denali National Park in Alaska.

The Northern Lights, Alaska

Lightning without clouds

Although we associate most, if not all of the lightning storms we see with the cumulonimbus cloud, it is possible to have lightning striking the ground with no cloud what so ever. Most recently, the eruption of the volcano Eyjafjallajokull in Iceland in April 2010 produced a visually stunning natural phenomenon. But how did it happen?

                                Eyjafjallajokull eruption

Volcanic activity can trigger lightning as the enormous quantities of material and gases exploding out into the atmosphere creates a dense plume of highly charged particles. When these charged particles come in contact with neutrally charged particles in the ash, electrons can flow and the ash becomes charged relative to the other particles - think of rubbing a balloon quickly against your head. The same type of charge is building up but on a massive scale. This causes flashes in an attempt to neutralise particles again.

The lightning can be in many forms such as bolt lightning, sheet lightning and St Elmo's fireball (ball lightning).

Are human factors the main causes in many natural disasters?

Hey everyone, I'm very excited about starting my first blog! Hope you like it, feedback is very welcome!

A few weeks ago I was set an essay similar to the title of this post, and through my research for the essay, I came to the conclusion that actually, many reasons behind drastic consequences of earth hazards are caused by human factors, despite it being a NATURAL disaster.

For example, in Venezuela, 1999, a mass movement caused the death of over 50,000 people. Yes, the reasons why the  disaster occurred were natural, 914 mm of rain fell over 2 weeks prior to the disaster caused the flash floods and mudslides. However, thousands of people were exposed unnecessarily to the risk of the disaster as homes were built on alluvial fans on the coast - which had formed due to previous floods and mudslides depositing sediment. Despite knowledge of other debris flows, houses were still built in that area, causing thousands of people and  buildings to be right in the line of fire. If this had not occurred, then many lives would have been saved and the natural hazard would not have caused such disastrous consequences.

                                          Venezuela debris flow, 1999
Another example is La Conchita, California, where there are constant mudflows, causing damages to buildings and some deaths, yet the locals refuse to move away from the hazard.

Of course, there are many natural hazards where the main consequences are due to physical factors. The Tsunami in the Indian Ocean in 2004 main factor was the scale of the disaster and that most of the areas that were affected did not think they would need protection from Tsunamis.

Yet, in many places around the world, people will live knowingly in the risk of earth hazards for simple reasons such as land near a volcano has fertile land, or that floodplains are flat and therefore easy to build on.