September 2024

Rapa Nui

Leave a Comment / Features, South America, World /

Crash Landing Imagine being a Nasa astronaut in the early 2000s. You launch from the Kennedy space center to rapturous applause from the crowds of south Florida. You successfully make orbit, perhaps to service the hubble space telescope or to deliver essential supplies to the International Space Station. Your mission is a success and you start the re-entry procedure. Everything seems fine for the first few minutes, but then things start to go wrong. There are technical malfunctions. Through a combination of sublime skills of the pilots and absolute luck you are still in one piece as the shuttle approaches low earth orbit. You’re getting close to commercial air travel altitudes and still no catastrophe.    You now have another problem. You are over the vastness of the Pacific ocean and have no chance of making it to the planned landing runway. Luckily, the clever people of Nasa thought of this eventuality.  Scattered throughout the world at semi-regular intervals are a series of emergency landing sites for exactly this eventuality. The pilots scan the charts, they find just such a runway, seemingly floating in the middle of the South Pacific. Minutes later, you successfully land at Matertivi airport. You have touched down and are still in one piece. You breathe the mother of all sighs of relief. But, where on earth are you? Where is this miracle runway sticking out of the ocean? You are of course, on the tiny island of Rapa Nui. Better known as Easter Island.    Luckily, the shuttle never had to make use of this or any of the 50 or so designated emergency landing sites. In avoiding this particular emergency, those astronauts  missed out on a fascinating island. Easter Island is one of the most isolated inhabited islands in the world. Located in the southeastern Pacific Ocean, it is 3512km from the South American mainland and 2,075 from its nearest inhabited neighbour. The island’s remote location, intriguing history, and unique cultural heritage make it a fascinating subject for study and exploration. This article explores Easter Island’s volcanic birth, its physical landscape, political structure, history, and cultural significance, including the world famous Moai statues and Birdman cults, as well as its modern-day status and tourism. Easter Island was formed by volcanic activity that began approximately three million years ago. The island’s creation is attributed to the Easter Hotspot, a volcanic hotspot in the Earth’s mantle that caused magma to rise and create volcanic eruptions. Over time, The eruptions broke the surface at Easter Island, as well as a number of other island chains such as the Sala y Gomez islands. The Three Volcanoes Easter Island is roughly triangular in shape, covering an area of 163.6 square kilometers (63.1 square miles). Its maximum length from east to west is about 24 kilometers (15 miles), and its maximum width from north to south is around 12 kilometers (7.5 miles). The island’s coastline is rugged, with numerous cliffs and rocky shores, and only a few sandy beaches. Terevak Terevaka, the youngest and largest of the three volcanoes, forms the northern portion of the island. It formed about 300,000 years ago. Its gentle slopes rises to 507 meters (1,663 feet), making it the highest point on Easter Island. Its commanding view and easy access makes the summit a popular attraction for tourists on both foot or horseback.  Poike Situated on the easternmost tip of the island, Poike is the second oldest volcano, with its formation dating back to approximately 2.5 million years ago. It is less eroded than Rano Kau and has a more distinct conical shape. The Poike peninsula is generally the least visited part of the island Rano Kau Whilst Poike and Terevaka may be taller in elevation, they lack the drama of the third peak. Rano Kau. Located in the southwestern part of the island, Rano Kau is the oldest of the three volcanoes, estimated to have formed around 2.5 million years ago. It features the largest crater of the three. Its steep sided cliffs raise 324 meters above the ocean beneath and its enormous crater contains one of just three natural bodies of fresh water on the island. The Pacific ocean is working relentlessly to reclaim the volcano and the south-west corner of the crater is slowly collapsing. Sitting on the south-west cliff, overlooking the islands of Motu Nui and Motu Iti is the ceremonial village of Orongo. Should our intrepid astronauts have needed to make use of Matertivi airport, they would have landed on a flat plain wedged between the base of Rano Kau and the only major town of Hanga Roa.  Whilst we list only three named volcanoes, in actual fact, the entire island is covered with calderas, lava tunnels and other volcanic structures such as the cinder cone of Puna Pau just outside the main town of Hanga Roa or the crater of Rano Raraku from which the stone moai were carved. Discovery Long before European contact, Easter Island was settled by Polynesian navigators. Over the course of possibly many centuries, the Polynesian people gradually spread eastwards from the western Pacific. The exact arrival at Easter Island is unknown, but some time between the 10th and 13th century AD,  an intrepid bunch of sailors led by the mythical (and possibly fictitious) Hotu Matu’a pointed their double hulled canoes to the horizon and set sail. They set sail from their home of Hiva, which has been claimed to be in the Marquesas Islands, Gambier islands, Mangareva island, and many other places in eastern Polynesia. The exact location of Hiva is probably lost to time. What we do know is that after possibly many days, they spotted land, and arrived at the picture postcard beach of Anakena. They called their new home Te-Pito-te-Henua, literally translated as “end of the land”. The beach at Anakena is one of the few areas of the Easter Island coastline where boats can safely land.  Whilst much of this original colonization shrouded in mystery, we can safely suppose

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The International Date Line

Leave a Comment / Features, Maps, World /

There’s an imaginary line that circles our planet. It’s a border, of sorts. It runs from pole to pole. Not a national border or country frontier, but its impact is just as profound to those countries that find themselves on either side of it. In order to understand why this line is so weird, and why it exists at all, we need to travel back to 1675 and half a world away to sleepy Greenwich and the establishment of the Royal Observatory.  The Royal observatory is an entire subject to itself, but it’s important to understand the impact that the observatory has had on world geography. For mariners and geographers before 1675, Latitude was a well understood concept. The earth was divided into 2 hemispheres with a line running exactly between the two. We know this line as the equator. Two additional lines of latitude were added in the form of the Tropics of Cancer and Capricorn. These are the two points at which the sun reaches its highest declination. Basically the point at which the sun can be seen directly overhead at its solstice Up until the foundation of the Greenwich observatory, there was no obvious line that longitude should run along. Amongst the many other things that the observatory was responsible for was the creation of the Prime Meridian.The Prime Meridian, which passes through Greenwich, was designated as 0° longitude. Run that line around the entire globe, bisecting the poles and, located at 180° longitude, you will find the International Date line (IDL). Its primary function is to accommodate the Earth’s rotation and the 24-hour day cycle, ensuring that when you cross it, the date changes by one day. Crossing from west to east results in going back a day, while crossing from east to west moves you forward by a day. So far, so simple, but from this fact onwards, international geography starts to take a back seat to international politics.  The Northern Reaches: The Arctic Ocean Head due south from the north pole along the international date line and the first land you hit is Wrangel Island, and the Russian Okrugs (Autonomous district) of Chukotka, if the IDL were to maintain a straight line it would move this district to the east of the IDL and separate it from the rest of Russia by one whole day. Further south, parts of the Alaskan Aleutian islands would suffer the same fate in the opposite direction. This was unacceptable to both countries. Here we have our first of many instances of geopolitics. The line bends, first east across the Chukchi sea and into the Bering strait. It dissects the Diomede islands, which, despite being just over 2 miles apart, are separated by a whole calendar day. Big Diomede, belonging to Russia being one calendar day ahead of little Diomede, which belongs to the USA. This unique situation often earns the islands the nickname “Tomorrow Island” (Big Diomede) and “Yesterday Island” (Little Diomede).   Once through the Bering strait, the date line takes a sharp turn to the west, ensuring that the St Lawrence island, and the entirety of the Aleutian archipelago remain on the same side of the line as the rest of Alaska. I think we can all agree that these minor deviations to maintain territorial integrity are fine. The deviations around Russia and USA caused roughly a 10° deviation first to the east, and then to the west of the IDL before settling back onto the correct longitude of 180° just south of Alaska.  The Northern Pacific Ocean For the next 5,500km, the IDL behaves itself. The line runs due south and encounters nothing but the depths of the pacific. The nearest it comes to anything at all is roughly 2,000km into it’s journey, when it passes Midway Atoll, venue of the famous world war 2 naval battle, roughly 250km to its east. By the time we reach the equator we’ve done literally half the globe with just minor deviations to avoid splitting countries in half. It’s at this point that things get interesting.  Moving south through the Pacific, over the equator and into the southern hemisphere, we find an increasing concentration of island nations, atolls, archipelagos and overseas territories. These islands have decisions to make in terms of their political and economic allegiances. You might think that being on the same side of the IDL as the USA would be economically advantageous, but this far south in the Pacific, the US mainland is prohibitively distant for such small economies to rely on. Kiribati: A Country in Two Time Zones The IDL next approaches the Republic of Kiribati, an island nation spread over a vast area of the central Pacific. Kiribati is an interesting case, it used to be bisected by the IDL, causing significant inconvenience. To address this, in 1995, Kiribati moved the IDL eastward to include the Line Islands within the same time zone as the rest of the country. This shift meant that the Line Islands, previously among the last places on Earth to see the new day, became the first. The result of this manoeuvre from Kiribati is that the IDL must thread a course keeping the tiny US Howard and Baker islands on its east, cross the equator and take a turn to the east, running parallel with the equator for over 2,000km. It then makes a turn to the north, and once again crosses the equator to encompass the island chains of Kiribati, before returning back to the south and west, all the while ensuring that the islands belonging to the Cook Islands nation and French Polynesia remain on the west of the IDL. The effect is that the IDL forms something resembling a hammerhead shark extending 2977 kilometres to the east that straddles the equator. Island nations spread throughout the Pacific Ocean Just south of the equator, The IDL returns to roughly 170° and heads south once more. The next islands it encounters are Samoa and American Samoa.

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Yellowstone

Leave a Comment / Features, North America, World /

Formation of a Supervolcano Tucked away in the very northeastern corner of Wyoming, and spilling out into Montana and Idaho is an area of outstanding natural beauty, beloved by tourists and natives alike. So beloved, in fact, that in 1872, President Ulysses S Grant declared it to be the first national park in the US and the second national Park on earth. We are, of course, talking of Yellowstone National Park. Scratch beneath the surface and you’ll find the Yellowstone hotspot, a plume of molten rock rising from deep within the Earth’s mantle. Interestingly, tectonic activity is causing the North America plate to slide over the magma chamber whilst the chamber itself stays put in relation to the center of the earth. As it does so, the magma chamber grows….and grows. Very occasionally, but ominously consistently, the magma chamber can grow no more and must release pressure in a violent eruption, the likes of which has not happened in the entire existence of human memory. The Yellowstone volcanic field has experienced three major eruptions in the past 2.1 million years: The Huckleberry Ridge Eruption (2.1 Million Years Ago) The first and largest of Yellowstone’s three major eruptions, known as the Huckleberry Ridge eruption, occurred approximately 2.1 million years ago. This eruption was truly colossal, ejecting an estimated 2,450 cubic kilometers (588 cubic miles) of volcanic material. To put this into perspective, Mount St. Helens ejected just 0.25 kilometres in its eruption of 1980. The Huckleberry Ridge eruption ejected 6000 times that amount of hot magma, ash and rock high up into the atmosphere.  If you were around 2.1 million years ago, the first thing you’re going to want to do is stand back. The caldera alone was 100km across. But don’t worry – even from many hundreds of kilometers away, you would be able to observe the 50km high plume of ejecta. It was colossal.  The ash and gases released into the atmosphere would have had profound climatic effects, likely killing every living organism within many hundreds of miles and causing a global volcanic winter for anything that survived. This period of global cooling would have drastically affected plant and animal life, leading to significant ecological disruptions.  The Huckleberry Ridge eruption created the Huckleberry Ridge Tuff, a widespread deposit of ash and pumice that can be seen in the geological record seeing the world. The eruption’s sheer volume caused the ground above the magma chamber to collapse, forming the massive caldera, one of the largest calderas on Earth.  The Mesa Falls Eruption (1.3 Million Years Ago) The second major eruption, known as the Mesa Falls eruption, took place around 1.3 million years ago. While smaller than the Huckleberry Ridge eruption, it was still a significant event, ejecting approximately 280 cubic kilometers (67 cubic miles) of volcanic material. The Mesa Falls eruption produced the Mesa Falls Tuff, another extensive deposit of ash and pumice. The eruption formed the Henry’s Fork Caldera, located in the Island Park region of Idaho, just west of the Yellowstone National Park boundary. This caldera measures approximately 45 kilometers (28 miles) in diameter. The climatic impact of the Mesa Falls eruption would have been less severe than that of the Huckleberry Ridge eruption, but it still would have caused significant environmental changes. The release of ash and gases into the atmosphere would have led to a short-term period of global cooling and disruptions in weather patterns. The Mesa Falls eruption highlights the cyclical nature of volcanic activity at Yellowstone. By studying the intervals between these major eruptions, geologists can better understand the behavior of the Yellowstone supervolcano and its potential future activity. The Lava Creek Eruption (640,000 Years Ago) The third and most recent major eruption, known as the Lava Creek eruption, occurred approximately 640,000 years ago. This eruption was responsible for creating the current Yellowstone Caldera, a prominent feature of the national park today. The Lava Creek eruption ejected around 1,000 cubic kilometers (240 cubic miles) of volcanic material. The Lava Creek eruption produced the Lava Creek Tuff, yet another widespread deposit of ash and pumice that blanketed much of North America. The collapse of the magma chamber following the eruption formed the Yellowstone Caldera, which measures approximately 70 kilometers (43 miles) in diameter. The climatic effects of the Lava Creek eruption would have been significant, with the release of ash and gases causing short-term cooling and disruptions to ecosystems. However, life gradually recovered, and the Yellowstone region has since been shaped by ongoing geothermal activity. The Lava Creek eruption provides a more recent example of a supereruption and its effects. The current geothermal features of Yellowstone, including world famous geysers, hot springs, and fumaroles, are a direct result of the heat and activity remaining from this last major eruption. These eruptions have shaped the landscape of the region, creating extensive lava flows, ash deposits, and the characteristic caldera. How to spot a Supervolcano The Yellowstone Supervolcano was identified through a combination of geological, geophysical, and geochemical studies. Early explorers and geologists noted the region’s extensive geothermal activity, but were unable to locate the caldera. but it wasn’t until the mid-20th century that the true nature of Yellowstone’s volcanic system was understood. Advances in seismic imaging, satellite technology, and other scientific tools showed that the entire central portion of the park was caldera.  The Yellowstone Caldera The caldera at Yellowstone was almost entirely formed by the final eruption, the Lava Creek eruption. Unlike most volcanoes, with their recognisable conical shape and caldera sat atop, The Yellowstone Caldera is massive. It’s simply too big to see in a single vista with the naked eye. The volcanic depression was formed during the final eruption not so much by the accumulation of materials around a central caldera as most volcanoes form, but rather by the literal collapse of earth as the staggering amount of materials were blown out into the atmosphere. The caldera, measuring approximately 55 by 72 kilometers (34 by 45 miles) doesn’t really project up into

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