Llullaillaco is a stratovolcano at the border of Argentina (Salta Province) and Chile. It lies in the Puna de Atacama, a region of very high volcanic peaks on a high plateau within the Atacama Desert, one of the driest places in the world. It is the fifth highest volcano in the world, and it is also the seventh highest mountain of the Western Hemisphere.

Llullaillaco follows the typical Puna de Atacama volcano pattern: it is surrounded by large debris fields, and is perpetually capped by snow and small glaciers despite the extremely dry conditions of the region.

The peak's name comes from Aymara "murky water": llulla= dirty and yacu= water. Other sources propose it to have originated from Quechua Lullac= lie, Yacu= water: "lying (or treacherous) water".

It has been confirmed that Incas climbed Llullaillaco in the pre-Columbian period. Artifacts on the summit constitute the highest evidence of human presence worldwide before the late nineteenth century. Also, the huáqueros may have also reached its summit and those of other mountains in the region during their searches. The first recorded ascent was on December 1, 1952, by Bión González and Juan Harseim.

Geology

Two major geological stages can be highlighted in the history of the volcano: Llullaillaco I, the ancestral primary volcano, dates back to the Pleistocene. Two very eroded cones with associated lava flows, up to 20 km in length, distributed mainly to the West, evidence these stages.

Built upon it there is a well preserved secondary post-glacial edifice called Llullaillaco II, which has been active during human history. Many Holocene lava flows are associated with this latter phase; the two most notable are directed North and South of the volcano. These youthful-looking dacitic flows have been dated to be of late Pleistocene age. Moreover, hot avalanche deposits, extending up to 3 km, are associated with one of the southern lava flows. There are still other very conspicuous flows remaining: one of the most striking, apparently caused by partial collapse of Lullaillaco I about 150,000 years ago, extends eastward into Argentina, diverging around Cerro Rosado stratovolcano 17 km to the East and terminating in the Salar del Llullaillaco. This deposit has not yet been thoroughly studied.

There are reports of eruptions in 1854, 1868, and 1877, possibly causing the youngest lava flows in the area, which are easily recognizable because of their very dark appearance.

Archaeology

During 1983-85 American archaeologist Dr Johan Reinhard directed three surveys of archaeological sites on the summit and slopes of the mountain.

In 1999 on Llullaillaco's summit, an Argentine-Peruvian expedition directed by Reinhard found the perfectly preserved bodies of three Inca children, sacrificed approximately 500 years earlier. This is the highest Inca burial so far discovered in Tawantinsuyu, and is the world's highest archaeological site.

According to contemporary writings by Spanish priests, these children were participants in capacocha, a sacrificial rite that occurred in celebration of key events in the life of the Inca emperor.

The mummies are those of a 15-year-old girl, nicknamed "La doncella" (The maiden), a seven-year-old boy, and a six-year-old girl, nicknamed "La niña del rayo" (The lightning girl). The latter's nickname reflects the fact that sometime in the 500 year period the mummy spent on the summit, it was struck by lightning, partially burning the preserved body and some of the ceremonial artifacts left with the mummies.

The three mummies are exhibited at the Museo de Arqueología de Alta Montaña in Salta, Argentina, in a rotating fashion, so as not to expose any of the mummies for too long a time at once. Mummies are typically rotated in the exhibit every six months.

credited to wikipedia

Lanín is an ice-clad, cone-shaped stratovolcano on the border of Argentina and Chile. It forms part of two national parks: Lanín in Argentina and Villarrica in Chile. It is a symbol of the Argentine province of Neuquén, being part of its flag and its anthem. Although the date of its last eruption is not known, it is estimated to have occurred within the last 10,000 years.

The ascent is regulated by the management of Argentine National Parks and the Argentine National Gendarmerie, and is relatively simple, but many deaths have occurred due to lack of responsibility and caution of the climbers. The nearest towns, usually employed as a base for climbers, are Pucón in Chile and Junín de los Andes in Argentina.

There are two paths to the summit: one on the north, starting at 1,200 above mean sea level near Lake Tromen and the international Mamuil Malal Pass, accessible via Neuquén's Provincial Route 60; and one on the south, starting beside Lake Huechulafquen, accessible via Provincial Route 61.

credited to wikipedia

Poás Volcano National Park, in Spanish Parque Nacional Volcán Poás, is a National Park that covers an area of approximately 16,000 acres (65 km²); the summit is 8,900 feet (2,708 m). One of the attractive features about Poás is that you can get all the way to the edge of the crater. The volcano is located in the Central Volcanic Conservation Area located in the Alajuela Province near the Pacific coast of Costa Rica, which encompasses the area around the Poás Volcano. The main crater is 950 feet (289 m) deep and is quite active with frequent small geyser and lava eruptions, however the last major eruptions were during 1952-54. Two more craters make up parts of the park, the extinct Von Frantzuis crater and the Botos crater. Botos is a beautiful cold, green water crater lake with a diameter of 1,200 feet (365 m). The Botos crater has not erupted for about 7,500 years. Well-marked trails will take you to see the two inactive craters. The park is frequently closed to visitors because of sulphuric gas emissions. There are a number of indications that the volcano is slowly building towards a new eruption over the last decade.

Flora and fauna

The park maintains a variety of wild plant and animal species, such as the Poas Magnolia tree, and Bangs's Mountain Squirrel. It is home to many bird species, including the Clay-colored Robin and the Resplendent Quetzal and varieties of hummingbirds, tanagers, flycatchers and toucans.

credited to wikipedia

Mount Wai’ale’ale ("rippling water" or "overflowing water" and also often spelt Waialeale in English without the ‘okina), elevation 5,148 feet (1,569 m), is a shield volcano and the second highest point on the island of Kaua’i in the Hawaiian Islands. Averaging more than 460 inches (12,000 mm) of rain over the last 32 years, with a record 683 inches (17,300 mm) in 1982, its summit is considered one of the rainiest spots on earth. It has been promoted in tourist literature for many years as the wettest spot, although the 38-year average at Mawsynram, Meghalaya, India is 11,873 millimetres (467.4 in). However, Mawsynram's rainfall is concentrated in the monsoon season, while the rain at Waialeale is more evenly distributed through the year.

Several factors give the summit of Waialeale more potential to create precipitation than the rest of the island chain:

1. Its northern position relative to the main Hawaiian Islands provides more exposure to frontal systems that bring rain during the winter.

2. It has a relatively round and regular conical shape, exposing all sides of its peak to winds and the moisture that they carry.

3. Its peak lies just below the so-called trade wind inversion layer of 6,000 feet (1,800 m), above which trade-wind-produced clouds cannot rise.

4. And most importantly, the steep cliffs cause the moisture-laden air to rise rapidly - over 3,000 feet (910 m) in less than 0.5 miles (0.80 km) - and drop a large portion of its rain in one spot, as opposed to spreading the rain out over a larger area if the slope were more gradual.

The great rainfall in the area produces the Alaka’i Wilderness Preserve, a large boggy area that is home to many rare plants. The ground is so wet that although trails exist, access by foot to the Waialeale area is extremely difficult.

credited to wikipedia and flickr: Jean & Abbott Luxury Kauai Vacation Rentals

Mount Tarawera is a volcanic mountain 24.1 kilometres southeast of Rotorua in the North Island of New Zealand. It consists of a series of rhyolitic lava domes that were fissured down the middle by an explosive basaltic eruption in 1886, which also killed over a hundred people. The peaks are Ruawahia Peak, Tarawera Peak and Wahanga Peak. The summit is at 1111 metres. The crater of the volcano is a series of chasms, running for 17 kilometres northeast-southwest.

The volcano is surrounded by a series of lakes, many of which were created or drastically altered in the 1886 eruption. These lakes include Lakes Tarawera, Rotomahana, Rerewhakaaitu, Okataina, Okareka, Tikitapu (Blue Lake) and Rotokakahi (Green Lake). The Tarawera River runs northeastwards across the northern flank of the mountain from Lake Tarawera.

The 1886 eruption

Shortly after midnight on the morning of 10 June 1886 a series of more than 30 increasingly strong earthquakes were felt in the Rotorua area and an unusual sheet lightning display was observed from the direction of Tarawera. At around 2:00 am[1] a larger earthquake was felt and followed by the sound of an explosion. By 2:30 am Mount Tarawera's three peaks had erupted, blasting three distinct columns of smoke and ash thousands of metres into the sky. At around 3.30 the largest phase of the eruption commenced with a large quantity of ejecta from Rotomahana, in the form of a pyroclastic surge obliterating the Pink and White Terraces and several villages within a 6 kilometre radius.

The eruption was heard clearly as far away as Blenheim and the effects of the ash in the air were observed as far south as Christchurch, over 800 km south. In Auckland the sound of the eruption and the flashing sky was thought by some to be an attack by Russian warships.

The eruption is believed to have killed around 120 people (including seven Europeans), although it is possible that many more people died. The eruption also destroyed the world famous Pink and White Terraces and buried many Māori villages, including Te Wairoa. Approximately 2 cubic kilometres of tephra was erupted, more than Mount St. Helens ejected in 1980. Many of the lakes surrounding the mountain had their shapes and areas dramatically altered, especially the eventual enlargement of Lake Rotomahana, the largest crater involved in the eruption, as it re-filled with water. The rift created during the eruption extends 17 km across the mountain, Lake Rotomahana and through the Waimangu Volcanic Rift Valley.

The phantom canoe

One pervasive legend of the 1886 eruption is that of the phantom canoe. 11 days before the eruption, a boat full of tourists returning from the Terraces saw what appeared to be a war canoe approach their boat, only to disappear in the mist half a mile from them. One of the witnesses was a clergyman. Nobody around the lake owned such a war canoe, and nothing like it had been seen on the lake for many many years.

Though skeptics maintained that it was a freak reflection seen on the mist, tribal elders at Te Wairoa claimed that it was a waka wairua (spirit canoe) and was a portent of doom.

It has been suggested that the waka was actually a freak wave on the water, caused by seismic activity below the lake, but locals believe that a future eruption will be signalled by the reappearance of the canoe.

credited to wikipedia

Mount Teide or, in Spanish, El Teide, is an active though dormant volcano which last erupted in 1909 from the El Chinyero vent on the Santiago (northwestern) rift and is located on Tenerife, Canary Islands. The volcano and its surrounds comprise the Teide National Park (Parque Nacional del Teide in Spanish). The park has an area of 18900 ha and was named a World Heritage Site by UNESCO on June 29, 2007.

At 3718 m above sea level, and approximately 7500 m above the floor of the Atlantic Ocean, Teide is the highest mountain in Spain and the highest point in the Atlantic Ocean. The island of Tenerife itself is the third largest volcanic ocean island on Earth by volume. Teide is also the third highest volcano on a volcanic ocean island. It is also unstable and possibly in a more advanced stage of deformation and failure than the much publicised Cumbre Vieja. The United Nations Committee for Disaster Mitigation have designated Teide as a Decade Volcano. It is considered to be the 13th most dangerous volcano in the world due to its proximity to several major towns and the nearby city of Puerto de la Cruz.

Teide together with its neighbour Pico Viejo and Montaña Blanca forms the Central Volcanic Complex.

Name

El Pico del Teide (The Peak of Teide) is the modern Spanish name attributed to the volcano. The Lunar mountain, Mons Pico, part of the Montes Teneriffe mountain range, situated in the inner ring of the lunar mare Imbrium, was named after this 18th Century version by Johann Schröter. Prior to the 1495 Spanish colonization of Tenerife, the native Guanches referred to the volcano as Echeyde . Echeyde, in the Guanches legends, meant some sort of powerful figure leaving the volcano that could turn into hell. The Guanches believed that Echeyde held up the sky.

Formation

The stratovolcanoes Teide and Pico Viejo are the most recent centres of activity on the volcanic island of Tenerife. Tenerife is the largest (2058 km2) and highest (3718 m) island in the Canaries and has a complex volcanic history. The formation of the island and development of the current Teide volcano can be summarised into five stages, as shown in the diagram to the right.

Stage One

Similar to the other Canary Islands, and Volcanic Ocean Islands in general, the island of Tenerife was built by accretion of three large Shield Volcanoes, which developed in a relatively short period of time. This early shield stage volcanism formed the bulk of the emerged part of Tenerife. The shield volcanoes date back to the Miocene and early Pliocene and are preserved in three isolated and deeply eroded massifs: Anaga (to the NE), Teno (to the NW) and Roque del Conde (to the south). Each individual shield was apparently constructed in less than three million years and the entire island in about eight million years.

Stages Two and Three

The initial juvenile stage was followed by a period of 2-3 million years of eruptive quiescence and erosion. This cessation of activity is typical of the Canaries, for example La Gomera is currently in this erosional stage. After this period of quiescence the volcanic activity became concentrated within two large edifices; the central volcano of Las Cañadas and the Anaga massif. The Las Cañadas volcano developed over the Miocene shield volcanoes and may have reached 40 km in diameter and a height of 4500 m.

Stage Four

Around 160-220 thousand years ago the summit of the Las Cañadas I volcano collapsed creating the Las Cañadas (Ucanca) caldera. Later a fresh stratovolcano - Las Cañadas II volcano reformed and underwent catastrophic collapse. Detailed mapping indicates that the site of this volcano was in the vicinity of Guajara. The Las Cañadas III volcano formed in the Diego Hernandez sector of the caldera. Detailed mapping indicates that all the Las Cañadas volcanoes attained a maximum altitude similar to that of Teide - which is also referred to as the Las Cañadas IV volcano

Two theories on the formation of the this 16 x 9 km caldera exist.

The first is that the depression is the result of a vertical collapse of the volcano. The collapse being triggered by the emptying of shallow (at or about sea level) magma chambers under the Las Cañadas volcano after large-volume explosive eruptions.

The second theory is that the caldera was formed by a series of lateral gravitational collapses, similar to those described in Hawaii. Evidence for the later theory has been found in both onshore observations and marine geology studies.

Stage Five

Historical volcanic activity on the island is associated with vents on the Santiago or NW (Boca Gangrejo 1492, Montaña Negras 1706, Narices del Teide or Chahorra 1798 and El Chiyero 1909) and the Cordillera Dorsal or NE (Siete Fuentes and Fasnia in 1704 and 1705) rifts. Historical activity associated with the Montaña Teide - Pico Viejo stratovolcanoes occurred in 1798 from the Narices del Teide on the western flank of Pico Viejo. Eruptive material from Pico Viejo-Montaña Teide-Montaña Blanca which partially fills the Las Cañadas caldera. The last explosive eruption involving the central volcanic centre was from Montaña Blanca ~2000 BP.

The rifts form prominent ridges running NE and NW through the island from the Las Cañadas caldera. Since the collapse, eruptive products from the rifts have filled the resulting embayment with increasingly evolved (differentiated lavas) mostly of phonolitic composition and finally developed the Teide and Pico Viejo stratovolcanoes, nested in the embayment itself.

The lava flows on the flanks of Teide weather to a very thin, but nutrient and mineral rich soil that supports a diverse amount of plant species. Vascular flora consists of 168 plant species, 33 of which are endemic to Tenerife.

Historical eruptions

Teide is currently dormant, the last eruption occurred in 1909 from the El Chinyero vent, on the Santiago Rift (northwest) which is aligned in a northwest-southeast direction. Small eruptions occurred in 1704, 1705 on the Dorsal Rift (northeast). The 1706 eruption from the Montaña Negras vent on the Santiago vent destroyed the town and principal port of Garachico, plus several smaller villages. The last eruption within the Las Cañadas caldera occurred in 1798 from the Narices del Teide or Chahorra (Teides Nostrils) on the western flank of Pico Viejo (Old Peak - which is actually younger than Teide). The eruption was predominantly strombolian in style and mostly a'a lava was erupted. These lavas are visible alongside the Vilaflor - Chio road.

The explorer Christopher Columbus reported seeing "... A great fire in the Orotava Valley...," as he sailed past the Tenerife on his voyage to discover the New World in 1492. This was interpreted as indicating that he had witnessed an eruption in the Orotava Valley.

Unfortunately radiometric dating of possible lavas disproved the eruption theory. However, radiometric dating indicates that an eruption did occur in 1492 from the Boca Gangrejo vent.

About 150,000 years ago, a much larger explosive eruption occurred, probably of Volcanic Explosivity Index 5. This eruption created the Las Cañadas caldera, a large caldera, at about 2,000 m above sea level. The caldera is ~16 km across east-west and ~9 km north-south. At Guajara, on the south side of the structure, the internal walls rise as almost sheer cliffs from 2,100 m to 2,715 m. The 3,718 m summit of Teide itself, and its sister stratovolcano, Pico Viejo 3,134 m, are both situated in the northern half of the caldera, and are derived from eruptions subsequent to this prehistoric explosion.

Further eruptions are possible at some future unascertainable date, including a risk of pyroclastic flows and surges similar to those that occurred at Mount Pelée, Merapi, Mount Vesuvius, Soufrière Hills, Mount Unzen, etc. During 2003, there was an increase in seismic activity at the volcano. Many volcanoes e.g. Mount St Helens, Soufrière Hills had similar sesimic activity prior to becoming active. Such actvity is considered as being indicative of magma rising into the edifice.

Teide is considered to be unstable and has a distinctive bulge on its northern flank. This bulge is not believed to be associated with an influx of magma, but the result of a slow northwards collapse of the edifice. Seismic evidence suggests that Teide may be constructed over the headwall scarp of the infilled Icod Valley, a massive landslide valley formed by edifice failure in a similar manner to that of the Güímar and Orotava Valleys. The summit of the volcano has a number of small active fumaroles emitting sulfur dioxide and other gases including low levels of hydrogen sulfide.

Flora and fauna

Forests of Canary Island Pine (Pinus canariensis) occur from 1000-2100 m, covering the middle slopes of the volcano, and having an alpine timberline 1000 m lower than that of continental mountains of similar latitude. At higher altitudes, the Las Canadas caldera provides sufficient shelter for more fragile species such as the Canary Island cedar (Juniperus cedrus), and the Canary Island pine (Pinus canariensis) to grow.

The most dominant plant species in the Teide National Park are the Teide white broom (Spartocytisus supranubius), which has a white and pink flower; the Canary Island wallflower (Erysimum scoparium), which has white and violet flowers; and the Teide bugloss (Echium wildpretii), whose red flowers form a pyramid up to 3m in height.The Teide Daisy (Argyranthemum teneriffae) can be found at altitudes close to 3,600m above sea level. The Teide Violet (Viola cheiranthifolia) can be found right up to the summit of the volcano, making it the highest flowering plant in Spain.

These plants are adapted to the tough environmental conditions on the volcano such as high altitude, intense sunlight, extreme temperature variations, and lack of moisture. Adaptations include acquiring semi-spherical forms, acquiring a downy or waxy cover, reducing the exposed leaf area, and having a high flower production. Flowering takes place in the late spring or early summer, in the months of May and June.

The Teide National Park contains a huge range of invertebrate Fauna, over 40% of which are endemic species, with 70 species only being found in the National Park. The invertebrate fauna include spiders, beetles, dipterans, hemipternas, and hymenopterae.

In contrast, Teide national park has only a limited variety of vertebrate fauna. Ten species of bird nest in the park. These include the blue chaffinch (Fringilla teydea teydea); Berthelot’s pipit (Anthus berthelotii berthelotii); the wild canary (Serinus canaria); and a species of kestrel (Falco tinnunculus canariensis).

Three endemic reptile species are also found in the park – the Canary Island Lizard (Gallotia galloti galloti), the Canary Island wall gecko (Tarentola delalandii), and the Canary Island skink (Chalcides viridanus viridanus). The only mammals native to the Park are bats, the most common species of which is Leisler’s bat (Nycatalus leisleri). Other mammals such as the mouflon, the rabbit, the house mouse, the black rat, the feral cat, and the Algerian Hedgehog have all been introduced to the park.

Access

The volcano and its surroundings, including the whole of the Las Cañadas caldera, are protected in a national park, the Parque Nacional del Teide. Access is by a public road running across the caldera from northeast to southwest. The public bus service TITSA runs a once per day return service to Teide from both Puerto de la Cruz and Playa de las Americas. A parador (hotel) is also within the National Park along with a small chapel. The Teleférico cable car goes from the roadside at 2,356 m most of the way to the summit, reaching 3,555 m. Each car carries 38 passengers (34 in high wind) and takes 8 minutes to reach the summit. In peak season, queues can exceed two hours. Access to the summit itself is restricted; a free permit (obtainable from the Park office in Santa Cruz, Calle Emilio Calzadilla, 5 - 4th floor) is required to climb the last 200 m. Numbers are normally restricted to 150 per day

Due to the altitude, oxygen levels are lower than at sea level. This can cause people with heart or pulmanory conditions to become light headed, dizzy, develop mountain sickness and in extreme cases unconsciousness. The only treatment is to return to lower altitudes and acclimatise.

credited to wikipedia

Ol Doinyo Lengai is a stratovolcano located in Northern Tanzania. It looms 9,524 feet above the East African Rift Valley. The name Ol Doinyo Lengai means "The Mountain of God" in the Maasai language. It is the only active volcano in Tanzania and one of a select few that are active in the East African Rift Valley. The volcano has erupted many times since it first began to be observed by geologists. Major eruptions have occurred in 1880, 1914-15, 1926, 1940-41, 1958, 1960-66, 1983-93, 1994-1998, and the mountain continues to erupt mildly to this day.

Geologic Processes

The lava produced at Ol Doinyo Lengai is unlike any other lava on earth. Unlike most lavas, the lava at Ol Doinyo Lengai has a very low silica content. The lava from Ol Doinyo Lengai is a carbonatite, meaning it has more than a fifty percent carbonate content. Carbonatites are quite uncommon in the geologic record, and even less common at the surface as a liquid. Carbonatites are usually found as intrusive dikes, volcanic plugs, or cone sheets. Furthermore, most carbonatites are calcite carbonatites, meaning that they are composed primarily of the mineral calcite, which is calcium carbonate. In contrast, the lava at Ol Doinyo Lengai is composed largely of sodium and potassium carbonate. Called natrocarbonatite, sodium and potassium carbonates are even more rare than calcite carbonatites.

The minerals that dominate the lava at Ol Doinyo Lengai are nyerereite and gregoryite, carbonates that contain a high percentage of sodium and potassium. Both of these minerals are anhydrous and react with moisture in the atmosphere very rapidly. As a result of this, the runny black lava that spits from the mountain quickly turns gray or white as the minerals absorb water.

The lack of bulky silica molecules in the lava at Ol Doinyo Lengai allows the melt to flow extremely easily, making it the least viscous lava on earth. The natrocarbonatites of Ol Doinyo Lengai stay liquid at extremely low temperatures (550 C) relative to normal basaltic lavas (1100 C) as a result, they can be studied closely without protective gear. This is one of the most intriguing aspects of Ol Doinyo Lengai to geologists.

Products of the Geologic Process

Most lavas on earth have a silica-rich basaltic or rhyolitic composition. Basaltic and rhyolitic lavas form when material from the crust and upper mantle melt and flow to the surface, essentially maintaining their chemical composition.

Carbonatite lavas do not represent typical mantle or crust composition. There are two dominant theories for explaining this. One theory proposes that they are formed in a ‘primary’ fashion. This means that they are the melted product of carbonate-rich rocks found in the crust. Essentially, this theory states that carbonatite volcanoes form where there is carbonate-rich rock that is melted to form lava. It is unlikely that this is the case, because carbonatites have been associated with alkali-rich parent rocks.

The second theory proposes that carbonatites are the result of a separation of magma into chemically separate units- a process called differentiation. One type of differentiation is liquid immiscibility. Silicate minerals are crystallized as a melt cools. Because carbonate is not included in silicate mineral formation, the relative abundance of carbonate builds up until the melt is supersaturated with respect to carbonate. At this point, the carbonate-saturated magma is able to physically separate itself from the rest of the magma. If the carbonate-saturated melt is then brought to the surface, it is possible to have a carbonate-rich lava.

Another type of differentiation that may occur at Ol Doinyo Lengai is fractional crystallization. In fractional crystallization, newly formed crystals float, sink, or are otherwise prevented from chemically interacting with the rest of the melt. Usually, iron and magnesium rich crystals form, leaving behind more silica and aluminum rich melt. In the case of Ol Doinyo Lengai, carbonate-enriched melt is left behind as silica bearing crystals are separated.

Both of these differentiation processes could result in the carbonatite lava that we see at Ol Doinyo Lengai. In reality, it is most likely that a combination of all three of these processes take place at Ol Doinyo Lengai. The differentiation of the magma beneath Ol Doinyo Lengai had probably been occurring long before Ol Doinyo Lengai was created. It was not until rifting began pulling the African continent apart that the carbonatite magma was able to reach the surface.

Impacts

Why is the study of Ol Doinyo Lengai important? First of all, Ol Doinyo Lengai is the world's only active carbonatite volcano. This makes it a very important site for the study of carbonatites. The world's largest deposits of rare earth elements (REEs) are found in carbonatite complexes. It is believed that REEs are rare because they cannot incorporate themselves into minerals when they form deep in the earth. REEs that cannot fit into silicate minerals are concentrated in the immiscible carbonate portion of the melt. This results in REEs present at the surface with carbonatites. The largest REE deposits in the world are in Bayan Obo, China and Mountain Pass, CA. Both of these locations have carbonatite complexes.

Another interesting impact of the study of natrocarbonatite lava at Ol Doinyo Lengai is its application to planetary geology. There are volcanic features on Venus that have characteristiscs of river systems on earth. These include meander bends, braded flow systems and deltas. It is suspected that the lava that created these features on Venus is similar to the lava produced at Ol Doinyo Lengai.

credited to earlham and wikipedia

The Ngorongoro Conservation Area or NCA is a conservation area situated 180 km (112 miles) west of Arusha in the Crater Highlands area of Tanzania. The conservation area is administered by the Ngorongoro Conservation Area Authority, an arm of the Tanzanian government, and its boundaries follow the boundary of the Ngorongoro Division of Ngorongoro District. It covers an area of 8,288 km² (3,200 square miles) - about the size of Crete.

History and geography

Based on fossil evidence found at the Olduvai Gorge, it is known that various hominid species have occupied the area for 3 million years. Hunter gatherers were replaced by pastorialists a few thousand years ago. The Mbulu came to the area about 2,000 years ago, and were joined by the Datoga around the year 1700. Both groups were driven from the area by the Maasai in the 1800s. Massive fig trees in the northwest of the Lerai Forest are sacred to the Maasai and Datoga people. Some of them may have been planted on the grave of a Datago leader who died in battle with the Maasai around 1840.

No Europeans are known to have set foot in the Crater until 1892, when it was visited by Dr. Oscar Baumann. Two German brothers farmed in the Crater until the outbreak of World War I, after leasing the land from the German colonial administration then in control of East Africa. Dr. Baumann shot three rhinos while camped in the crater, and the German brothers regularly organized shooting parties to entertain their German friends. They also attempted to drive the wildebeest herds out of the crater.

The Ngorongoro area originally was part of the Serengeti National Park when it was created by the British in 1951. Maasai continued to live in the newly created park until 1959, when repeated conflicts with park authorities over land use led the British to evict them to the newly declared Ngorongoro Conservation Area.

The Ngorongoro Conservation Area Authority is the governing body regulating use and access to the NCA. The area became a UNESCO World Heritage Site in 1979.

Land in the conservation area is multi-use, it is unique in Tanzania as the only conservation area providing protection status for wildlife whilst allowing human habitation. As such land use is controlled to prevent negative effects on the wildlife population, for example cultivation is prohibited at all but subsistence levels.

The area is part of the Serengeti ecosystem, and to the north-west, it adjoins the Serengeti National Park and is contiguous with the southern Serengeti plains, these plains also extend to the north into unprotected Loliondo division and are kept open to wildlife through trans-human pastoralism practiced by Maasai. The south and west of the area are volcanic highlands, including the famous Ngorongoro Crater and the lesser known Empakai. The southern and eastern boundaries are approximately defined by the rim of the Great Rift Valley wall, which also prevents animal migration in these directions.

The annual ungulate migration passes through the NCA, with wildebeest and zebra moving south into the area in December and moving north in June. This movement changes seasonally with the rains, but the migration will traverse almost the entire plains in search of food. The NCA has a healthy resident population of most species of wildlife, in particular the Ndutu Lake area to the west has strong cheetah and lion populations.

Wildlife

A population of approximately 25,000 large animals, largely ungulates along with reputedly the highest density of mammalian predators in Africa, lives in the crater. These include the black rhinoceros, whose local population declined from about 108 in 1964-66 to between 11-14 in 1995, and the hippopotamus, which is very uncommon in the area. There also are many other ungulates: the wildebeest (7,000 estimated in 1994), the zebra (4,000), the eland, and Grant's and Thomson's gazelles (3,000).

The crater has the densest known population of lions, numbering 62 in 2001. On the crater rim are leopards, elephants - numbering 42 in 1987 but only 29 in 1992 - mountain reedbuck, and buffalo (4,000 in 1994).

However, since the 1980s the crater's wildebeest population has fallen by a quarter to about 19,000 and the numbers of eland and Thomson’s gazelle also have declined while the buffalo population has increased greatly, probably due to the long prevention of fire which favors high-fibrous grasses over shorter, less fibrous types.

In summer, enormous numbers of Serengeti migrants pass through the plains of the reserve, including 1.7 million wildebeest, 260,000 zebra, and 470,000 gazelles. Waterbuck occur mainly near Lerai Forest; servals occur widely in the crater and on the plains to the west. Common in the reserve are lions, hartebeest, spotted hyenas and jackals. Cheetahs, although common in the reserve, are scarce in the crater itself. The African Wild Dog has recently disappeared from the crater and may have declined elsewhere in the Conservation Area as well.

Ngorongoro Crater

The main feature of the NCA is the Ngorongoro Crater, which is the world's largest unbroken, unflooded volcanic caldera. The Crater, which formed when a giant volcano exploded and collapsed on itself some two to three million years ago, is 610 m (2,001 ft) deep and its floor covers 260 km² (102 square miles). Estimates of the height of the original volcano range from fifteen to nineteen thousand feet (4500 to 5800 metres) high.

Although thought of as "a natural enclosure" for a very wide variety of wildlife, up to 20% or more of the wildebeest and half the zebra populations vacate the Crater in the wet season. However, an effect of this 'enclosure' situation means that the population of Ngorongoro lions is severely inbred, with many genetic problems passed from generation to generation. This is due to the very small amount of new bloodlines that enter the local gene pool, with very few migrating male lions entering the crater from the outside. Animal populations in the crater include most of the species found in East Africa, but there are no impalas, topis, oribis, giraffes, or crocodiles.

The crater highlands on the side facing the easterly trade winds receives 800–1200mm of rain a year and is covered largely in montane forest, while the less-steep west wall receives only 400–600 mm; this side is grassland and bushland dotted with Euphorbia bussei trees. The crater floor is mostly open grassland with two small wooded areas dominated by Acacia xanthophloea.

The Munge Stream drains Olmoti Crater to the north, and is the main water source draining into the seasonal salt lake in the center of the Crater. This lake is known by two names: Makat as the Maasai called it, meaning salt; and Magadi. The Lerai Stream drains the humid forests to the south of the Crater, and it feeds the Lerai Forest on the Crater floor - when there is enough rain, the Lerai drains into Lake Magadi as well. Extraction of water by lodges and NCA headquarters reduces the amount of water entering Lerai by around 25%.

The other major water source in the Crater is the Ngoitokitok Spring, near the eastern Crater wall. There is a picnic site here open to tourists and a huge swamp fed by the spring, and the area is inhabited by hippopotamus, elephants, lions, and many others. Many other small springs can be found around the Crater floor, and these are important water supplies for the animals and local Masaai, especially during times of drought.

Aside from herds of zebra, gazelle, and wildebeest, the crater is home to the "big five" of rhinoceros, lion, leopard, elephant, and buffalo. The crater plays host to almost every individual species of wildlife in East Africa, with an estimated 25,000 animals within the crater.

Following the recommendations of the ad hoc committee of scientists convened after the 2000 drought, an ecological burning program was implemented in the Crater, which entails annual or biannual controlled burns of up to 20% of the grasslands. Maasai are now permitted to graze their cattle within in the Crater, but must enter and exit daily.

credited to wikipedia and flickr: mar is sea Y

Krakatoa (Indonesian: Krakatau), also spelled Krakatao, is a volcanic island in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island (also called Rakata), and the volcano as a whole.

Significance

Its best known eruption culminated in a series of massive explosions on August 26–27, 1883, which was among the most violent volcanic events in modern times. With a Volcanic Explosivity Index of 6, it was equivalent to 200 megatons of TNT — about 13,000 times the yield of the Little Boy bomb (13 to 16 KT) that devastated Hiroshima, Japan, and four times the yield of the Tsar Bomba (50 MT), the largest nuclear weapon ever built. The 1883 eruption ejected approximately 21 cubic kilometres (5.0 cu mi) of rock, ash, and pumice, and generated the loudest sound historically reported: the cataclysmic explosion was distinctly heard as far away as Perth in Australia approx. 1,930 miles (3,110 km), and the island of Rodrigues near Mauritius approx. 3,000 miles (5,000 km) distant. Near Krakatoa, according to official records, 165 villages and towns were destroyed and 132 seriously damaged, at least 36,417 (official toll) people died, and many thousands were injured by the eruption, mostly from the tsunamis that followed the explosion. The eruption destroyed two-thirds of the island of Krakatoa.

Eruptions at the volcano since 1927 have built a new island in the same location, named Anak Krakatau (Indonesian: "Child of Krakatoa"). This island currently has a radius of roughly 2 kilometres (1.2 mi) and a high point around 300 metres (980 ft) above sea level, growing 5 metres (16 ft) each year.

Origin and spelling of the name

Although there are earlier descriptions of an island in the Sunda Strait with a "pointed mountain", the earliest mention of Krakatoa by name in the Western world was on a 1611 map by Lucas Janszoon Waghenaer, who labeled the island "Pulo Carcata". ("Pulo" is a form of pulau, the Indonesian word for "island".) About two dozen variants have been found, including 'Crackatouw', 'Cracatoa', and 'Krakatao' (in an older Portuguese-based spelling). The first known appearance of the spelling 'Krakatau' was by Wouter Shouten, who passed by "the high tree-covered island of Krakatau" in October 1658.

The origin of the Indonesian name Krakatau is uncertain. The main theories are:

* Onomatopoeia, imitating the noise made by cockatoos ('Kakatoes') which used to inhabit the island. However, Van den Berg points out that these birds are found only in the "eastern part of the archipelago" (meaning the Lesser Sundas, east of Java).

* From Sanskrit karka or karkata or karkataka, meaning "lobster" or "crab". ("Rakata" is also "crab" in the older Javan language.) This is considered the most likely origin.

* The closest Malay word is kelakatu, meaning "white-winged ant". Furneaux points out that in pre-1883 maps Krakatoa does somewhat resemble an ant seen from above with Lang and Verlaten lying to the sides like wings.

* Van den Berg (1884) recites a story that Krakatau was the result of a linguistic error. According to the legend, a visiting ship's captain asked a local inhabitant the island's name, and the latter replied "Kaga tau" (Aku nggak tau) — a Jakartan/Betawinese slang phrase meaning "I don't know". This story is largely discounted; it closely resembles other linguistic myths about the origin of the word kangaroo and the name of the Yucatán Peninsula.

There are two generally accepted modern spellings, Krakatoa and Krakatau. The origin of the English spelling Krakatoa is unclear, but may have been the result of a typographical error made in a British source reporting on the massive eruption of 1883. Also, like Egypt a couple of decades earlier, Polynesia (South Pacific) was in vogue in the late 19th century and the Polynesian-like suffix "-oa" (as in Samoa) may have caught on as a result. While Krakatoa is more common in the English-speaking world, the Indonesian Krakatau tends to be favored by others, including geologists. Verbeek seems to have started the modern convention of using "Krakatau" for the island proper and reserving "Rakata" for the main cone.

Geographical setting

Indonesia has over 130 active volcanoes, the most of any nation. They make up the axis of the Indonesian island arc system, which was produced by northeastward subduction of the Indo-Australian Plate. A majority of these volcanoes lie along Indonesia's two largest islands, Java and Sumatra. These two islands are separated by the Sunda Straits, which are located at a bend in the axis of the island arc. Krakatoa is directly above the subduction zone of the Eurasian Plate and Indo-Australian Plate where the plate boundaries make a sharp change of direction, possibly resulting in an unusually weak crust in the region.

Before the 1883 eruption, Krakatoa comprised three main islands: Lang ('Long', now called Rakata Kecil or Panjang) and Verlaten ('Forsaken' or 'Deserted', now Sertung), which were edge remnants of a previous very large caldera-forming eruption; and Krakatoa itself, an island 9 km (5.6 mi) long by 5 km (3.1 mi) wide. Also there was a tree-covered islet near Lang named Poolsche Hoed ('Polish Hat', apparently because it looked like one from the sea), and several small rocks or banks between Krakatoa and Verlaten. There were three volcanic cones on Krakatoa: Rakata (820 m/2,700 ft) to the south, Danan (450 m/1,500 ft), and Perboewatan (120 m/390 ft) to the north (Danan may have been a twin volcano).

Pre-1883 history

At some point in Prehistory, an earlier caldera-forming eruption occurred, leaving as remmants Verlaten, Lang, Polish Hat, and the base of Rakata. Later, at least two more cones (Perboewatan and Danan) formed, and eventually joined with Rakata, forming the main island of Krakatoa. The dating of these events is currently unknown; the Sunda Strait was first mentioned by Arab sailors around 1100 AD.

Subsequent volcanism

Anak Krakatau

Verbeek, in his report on the eruption, predicted that any new activity would manifest itself in the region which had been between Perboewatan and Danan. This prediction came true in 29 December 1927 when evidence of a submarine eruption was seen in this area (an earlier event in the same area had been reported in June 1927). A few days later, a new island volcano, named Anak Krakatau ("Child of Krakatoa"), broke water. Initially, the eruptions were of pumice and ash, and it (and 2 later islands) was quickly eroded away by the sea; but eventually Anak Krakatau #4 (broke water in August 1930) produced lava flows faster than the waves could erode them. Of considerable interest to volcanologists, this has been the subject of extensive study.

Current activity

Since the 1950s, Anak Krakatau has grown at an average rate of five inches (13 cm) per week. The island is still active, with its most recent eruptive episode having begun in 1994. Since then, quiet periods of a few days have alternated with almost continuous Strombolian eruptions, with occasional much larger explosions.

The most recent eruption began in April 2008, when hot gases, rocks, and lava were released. Scientists monitoring the volcano have warned people to stay out of a 3 km zone around the island.

Biological research

The islands have become a major case study of island biogeography and founder populations in an ecosystem being built from the ground up in an environment virtually sterilized.

The islands had been little explored or surveyed before the 1883 catastrophe- only two pre-1883 biological collections are known: one of plant specimens and the other part of a shell collection. From descriptions and drawings made by the HMS Discovery, the flora appears to have been representative of a typical Javan tropical climax forest. The pre-1883 fauna is virtually unknown, but was probably typical of the smaller islands in the area.

The 'Krakatau problem'

Biologically, the 'Krakatau problem' refers to the question of whether the islands were completely sterilized by the 1883 eruption or whether some life survived. When the first researchers reached the islands in May 1884, the only living thing they found was a spider in a crevice on the south side of Rakata. Life has quickly recolonized the islands, however- Verbeek's visit in October 1884 found grass shoots already growing. The eastern side of the island has been extensively vegetated by trees and shrubs, presumably brought there as seeds washed up by ocean currents or carried in birds' droppings (or brought by natives and scientific investigators). It is, however, in a somewhat fragile position and the vegetated area has been badly damaged by recent eruptions.

Handl's occupancy

A German, Johann Handl, obtained a permit to mine pumice in October 1916 (Thornton). His lease was for 8.7 square kilometres (3.4 sq mi), which was basically the eastern half of the island, for 30 years. He occupied the south slope of Rakata from 1915 to 1917, when he left due to "violation of the terms of the lease." (Winchester gives the date of Handl's leaving as late 1917–1921.) Handl built a house and planted a garden with "4 European families and about 30 coolies". He is also believed to have introduced Rattus rattus (Black Rat). He also found unburned wood below the 1883 ash deposits when digging, and fresh water was found below 18 feet (5.5 m).

National park

After Handl's departure, the western half of Rakata and Verlaten were designated a national monument in July 1919. The eastern half was added in 1925, and the islands were included in the Ujung Kulon Reserve, which had been established in 1921. In 1982, Ujung Kulon was made a national park. This led to a political problem since the Krakatoa Islands are politically controlled by the Lampung province of Sumatra, but part of a Javan park. This paradox was resolved in 1990, when Krakatoa was made a separate nature reserve. Park Rangers have a station on Sertung, from which they patrol, but as of 1996, they have no permanent patrol boats.

Credited to wikipedia and flickr:flydime