UK floods

There will be an update comming soon!!!

Setting the World on Fire!

whilst reading Yahoo news today i saw an article on a "fire Tornado"
http://uk.news.yahoo.com/setting-the-world-on-fire-stunning-pictures-of-rare-devil-tornado-emerge.html

So i thought i would explain what a fire tornado is and why hey are so rare. !!!!

A fire whirl, colloquially fire devil or fire tornado, is a phenomenon—rarely captured on camera—in which a fire, under certain conditions (depending on air temperature and currents), acquires a vertical vorticity and forms a whirl, or a tornado-like vertically oriented rotating column of air. Fire whirls may be whirlwinds separated from the flames, either within the burn area or outside it, or a vortex of flame, itself.

An extreme example is the 1923 Great Kantō earthquake in Japan which ignited a large city-sized firestorm and produced a gigantic fire whirl that killed 38,000 in fifteen minutes in the Hifukusho-Ato region of Tokyo. Another example is the numerous large fire whirls (some tornadic) that developed after lightning struck an oil storage facility near San Luis Obispo, California on April 7, 1926, several of which produced significant structural damage well away from the fire, killing two. Thousands of whirlwinds were produced by the four-day-long firestorm coincident with conditions that produced severe thunderstorms, in which the larger fire whirls carried debris 5 kilometers away.

Most of the largest fire tornados are spawned from wildfires. They form when a warm updraft and convergence from the wildfire are present. They are usually 10-50 meters tall, a few meters wide, and last only a few minutes. However, some can be more than a kilometer tall, contain winds over 160 km/h, and persist for more than 20 minutes.

Fire whirls can uproot trees up to 15 metres (49 ft) tall. These can also aid the 'spotting' ability of wildfires to propagate and start new fires.

Visually impressive fire whirls may be encountered during dry wind gusts at the annual Burning Man festival in Nevada's Black Rock Desert, late on Saturday or Sunday evening during the burning of The Man or Temple, respectively.

The San Andreas Fault

Well... i assume that those of you who are reading this blog... at least some of you will be awere of the number of small earthquakes in northern calefornia and also ofshore.

(  as much as i would like to say that these little quakes are the predecessors of the so called and much freaked out about "BIG ONE" at the risk of getting into trouble about it im not going to!!!!) so therefore im crossing this out.

these have therefore made me think of the best known fault in the world. The San Andreas fault on the east coast. this fault has been used anything from bond films (A View to a Kill) to the actuall reason for the richnes of the land that lies along it.

the san andreas fault has provided the majority of the west coast's wealth... from the fertile soil that grows the famous calafornian wines to the oil that bubbles up out of the ground. all of these things including the scenery are what bring in billions of dollars each year.... and the reason that people have chosen to settle here. It has been estimated that when the "Big One" hits... the estimated damage of around 100,000,000 dollars worth of damage could be paid for in under 2 years. proof that the advantages outweigh the downfalls.

Any way....

The San Andreas Fault is a continental transform fault that runs a length of roughly 810 miles (1,300 km) through California in the United States. The fault's motion is right-lateral strike-slip (horizontal motion). It forms the tectonic boundary between the Pacific Plate and the North American Plate.

The fault was first identified in Northern California by UC Berkeley geology professor Andrew Lawson in 1895 and named by him after a small lake which lies in a linear valley formed by the fault just south of San Francisco, the Laguna de San Andreas. After the 1906 San Francisco Earthquake, Lawson also discovered that the San Andreas Fault stretched southward into southern California. Large-scale (hundreds of miles) lateral movement along the fault was first proposed in a 1953 paper by geologists Mason Hill and Thomas Dibblee.

The San Andreas Fault can be divided into three segments.

Southern segment

The southern segment (known as the Mojave segment) begins near Bombay Beach, California. Box Canyon, near the Salton Sea, contains upturned strata resulting from that section of the fault.[2] The fault then runs along the southern base of the San Bernardino Mountains, crosses through the Cajon Pass and continues to run northwest along the northern base of the San Gabriel Mountains. These mountains are a result of movement along the San Andreas Fault and are commonly called the Transverse Range. In Palmdale, a portion of the fault is easily examined as a roadcut for the Antelope Valley Freeway runs directly through it.

After crossing through Frazier Park, the fault begins to bend northward. This area is referred to as the "Big Bend" and is thought to be where the fault locks up in Southern California as the plates try to move past each other. This section of the fault has an earthquake-recurrence interval of roughly 140–160 years. Northwest of Frazier Park, the fault runs through the Carrizo Plain, a long, treeless plain within which much of the fault is plainly visible. The Elkhorn Scarp defines the fault trace along much of its length within the plain.

Research has shown that the Southern segment, which stretches from Parkfield in Monterey County, California all the way down to the Salton Sea, is capable of a Richter scale 8.1 earthquake. An earthquake of that size on the Southern segment (which, at its closest, is 40 miles away from Los Angeles) would kill thousands of people in Los Angeles, San Bernandino, Riverside, and other areas, and cause hundreds of billions of dollars in property and economic damage.

Central segment

The central segment of the San Andreas fault runs in a northwestern direction from Parkfield to Hollister. While the southern section of the fault and the parts through Parkfield experience earthquakes, the rest of the central section of the fault exhibits a phenomenon called aseismic creep, where the fault slips continuously without causing earthquakes.

Map showing the San Andreas (reds and orange) and major "sister" faults in the San Francisco Bay Area

Northern segment

The northern segment of the fault runs from Hollister, through the Santa Cruz Mountains, epicenter of the 1989 Loma Prieta earthquake, then on up the San Francisco Peninsula, where it was first identified by Professor Lawson in 1895, then offshore at Daly City near Mussel Rock. This is the approximate location of the epicenter of the 1906 San Francisco earthquake. The fault returns onshore at Bolinas Lagoon just north of Stinson Beach in Marin County. It returns underwater through the linear trough of Tomales Bay which separates the Point Reyes Peninsula from the mainland, runs just east of the Bodega Heads through Bodega Bay and back underwater, returning onshore at Fort Ross. (In this region around the San Francisco Bay Area several significant "sister faults" run more-or-less parallel, and each of these can create significantly destructive earthquakes.) From Fort Ross the northern segment continues overland, forming in part a linear valley through which the Gualala River flows. It goes back offshore at Point Arena. After that, it runs underwater along the coast until it nears Cape Mendocino, where it begins to bend to the west, terminating at the Mendocino Triple Junction.



The evolution of the San Andreas dates back to the mid Cenozoic, to about 30 Mya (million years ago). At this time, a spreading center between the Pacific Plate and the Farallon Plate (which is now mostly subducted, with remnants including the Juan de Fuca Plate, Rivera Plate, Cocos Plate, and the Nazca Plate) was beginning to interact with the subduction zone off the western coast of North America. The relative motion between the Pacific and North American Plates was different from the relative motion between the Farallon and North American Plates, so when the spreading ridge was 'subducted', a new relative motion caused a new style of deformation. This style is chiefly the San Andreas Fault, but also includes a possible driver for the deformation of the Basin and Range, separation of Baja California, and rotation of the Transverse Range.

The San Andreas Fault proper, at least the Southern Segment, has only existed for about 5 million years. The first known incarnation of the southern part of the fault was Clemens Well-Fenner-San Francisquito fault zone around 22–13 Ma. This system added the San Gabriel Fault as a primary focus of movement between 10–5 Ma. Currently, it is believed that the modern San Andreas will eventually transfer its motion toward a fault within the Eastern California Shear Zone. This complicated evolution, especially along the southern segment, is mostly caused by either the "Big Bend" and/or a difference in the motion vector between the plates and the trend of the fault(s).

Plate movement

All land west of the fault on the Pacific Plate is moving slowly to the northwest while all land east of the fault is moving southwest (relatively southeast as measured at the fault) under the influence of plate tectonics. The rate of slippage averages approximately 33 to 37 millimetres (1.3 to 1.5 in) annually across California.

The westward component of the motion of the North American Plate creates compressional forces which are expressed as uplift in the Coast Ranges. Likewise, the northwest motion of the Pacific Plate creates significant compressional forces where the North American Plate stands in its way, creating the Transverse Ranges in Southern California, and to a lesser, but still significant, extent the Santa Cruz Mountains, site of the Loma Prieta Earthquake of 1989.

Studies of the relative motions of the Pacific and North American plates have shown that only about 75 percent of the motion can be accounted for in the movements of the San Andreas and its various branch faults. The rest of the motion has been found in an area east of the Sierra Nevada mountains called the Walker Lane or Eastern California Shear Zone. The reason for this is not as yet clear, although several hypotheses have been offered and research is ongoing. One hypothesis which gained some currency following the Landers Earthquake in 1992 is that the plate boundary may be shifting eastward, away from the San Andreas to the Walker Lane.

Assuming the plate boundary does not change as hypothesized, projected motion indicates that the landmass west of the San Andreas Fault, including Los Angeles, will eventually slide past San Francisco, then continue northwestward toward the Aleutian Trench, over a period of perhaps twenty million years.

A study completed by Yuri Fialko in 2006 has demonstrated that the San Andreas fault has been stressed to a level sufficient for the next "big one," as it is commonly called; that is, an earthquake of magnitude 7.0 or greater. The study also concluded that the risk of a large earthquake may be increasing more rapidly than researchers had previously believed. Fialko also emphasized in his study that, while the San Andreas Fault had experienced massive earthquakes in 1857 at its central section and in 1906 at its northern segment (the 1906 San Francisco earthquake), the southern section of the fault has not seen a similar rupture in at least 300 years.

If such an earthquake were to occur, Fialko's study stated, it would result in substantial damage to Palm Springs and a number of other cities in San Bernardino, Riverside and Imperial counties in California, and Mexicali municipality in Baja California. Such an event would be felt throughout much of Southern California, including densely populated areas of metropolitan San Bernardino, Los Angeles, Orange County, San Diego, Ensenada and Tijuana, Baja California, San Luis Rio Colorado in Sonora and Yuma, Arizona.

"The information available suggests that the fault is ready for the next big earthquake but exactly when the triggering will happen and when the earthquake will occur we cannot tell," Fialko said. "It could be tomorrow or it could be 10 years or more from now," he concluded in September 2005.

Cascadia connection

Recent studies of past earthquake traces on both the northern San Andreas Fault and the southern Cascadia subduction zone indicate a correlation in time which may be evidence that quakes on the Cascadia subduction zone may have triggered most of the major quakes on the northern San Andreas during at least the past 3,000 years or so. The evidence also shows the rupture direction going from north to south in each of these time-correlated events. The 1906 San Francisco earthquake seems to have been a major exception to this correlation, however, as it was not preceded by a major Cascadia quake, and the rupture moved mostly from south to north

so... there you go... The San Andreas Fault.

The Grand Canyon

The Grand Canyon!

The Grand Canyon is a huge fissure in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata, and is also one of the 19 distinct physiographic sections of the Colorado Plateau province. It is not the deepest canyon in the world (Kali Gandaki Gorge in Nepal is far deeper), nor the widest (Capertee Valley in Australia is about 0.6 mi/1 km wider and longer than Grand Canyon); however, the Grand Canyon is known for its visually overwhelming size and its intricate and colorful landscape. Geologically it is significant because of the thick sequence of ancient rocks that are beautifully preserved and exposed in the walls of the canyon. These rock layers record much of the early geologic history of the North American continent.

Uplift associated with mountain formation later moved these sediments thousands of feet upward and created the Colorado Plateau. The higher elevation has also resulted in greater precipitation in the Colorado River drainage area, but not enough to change the Grand Canyon area from being semi-arid. The uplift of the Colorado Plateau is uneven, and the Kaibab Plateau that Grand Canyon bisects is over a thousand feet higher at the North Rim (about 1,000 ft/300 m) than at the South Rim. Almost all runoff from the North Rim (which also gets more rain and snow) flows toward the Grand Canyon, while much of the runoff on the plateau behind the South Rim flows away from the canyon (following the general tilt). The result is deeper and longer tributary washes and canyons on the north side and shorter and steeper side canyons on the south side.


Temperatures on the North Rim are generally lower than the South Rim because of the greater elevation (averaging 8,000 ft/2,438 m above sea level). Heavy rains are common on both rims during the summer months. Access to the North Rim via the primary route leading to the canyon (State Route 67) is limited during the winter season due to road closures. Views from the North Rim tend to give a better impression of the expanse of the canyon than those from the South Rim.


The Colorado River basin (of which the Grand Canyon is a part) has developed in the past 40 million years. A recent study places the origins of the canyon beginning some 17 million years ago. Previous estimates had placed the age of the canyon at 5 to 6 million years. The study, which was published in the journal Science in 2008, used uranium-lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon. There is a substantial amount of controversy because this research suggests such a substantial departure from prior widely supported scientific consensus.


The result of all this erosion is one of the most complete geologic columns on the planet.


The major geologic exposures in the Grand Canyon range in age from the 2 billion year old Vishnu Schist at the bottom of the Inner Gorge to the 230 million year old Kaibab Limestone on the Rim. There is a gap of about one billion years between the stratum that is about 500 million years old and the lower level, which is about 1.5 billion years old. This large unconformity indicates a period of erosion between two periods of deposition.

Many of the formations were deposited in warm shallow seas, near-shore environments (such as beaches), and swamps as the seashore repeatedly advanced and retreated over the edge of a proto-North America. Major exceptions include the Permian Coconino Sandstone, which contains abundant geological evidence of aeolian sand dune deposition. Several parts of the Supai Group also were deposited in non–marine environments.

The great depth of the Grand Canyon and especially the height of its strata (most of which formed below sea level) can be attributed to 5,000 to 10,000 feet (1500 to 3000 m) of uplift of the Colorado Plateau, starting about 65 million years ago (during the Laramide Orogeny). This uplift has steepened the stream gradient of the Colorado River and its tributaries, which in turn has increased their speed and thus their ability to cut through rock (see the elevation summary of the Colorado River for present conditions).

Weather conditions during the ice ages also increased the amount of water in the Colorado River drainage system. The ancestral Colorado River responded by cutting its channel faster and deeper.

The base level and course of the Colorado River (or its ancestral equivalent) changed 5.3 million years ago when the Gulf of California opened and lowered the river's base level (its lowest point). This increased the rate of erosion and cut nearly all of the Grand Canyon's current depth by 1.2 million years ago. The terraced walls of the canyon were created by differential erosion.

Between three million and 100,000 years ago, volcanic activity deposited ash and lava over the area which at times completely obstructed the river. These volcanic rocks are the youngest in the canyon.

Nevado del Ruiz... Its Back

Volcano Name- Nevado del Ruiz

Volcano Type- strata volcano

location- colombia

• The Colombian volcano Nevado del Ruiz is an active  stratovolcano with a history of generating deadly volcanic mudflows lahars- from relatively small-volume eruptions.
• In 1595, a lahar swept down the valleys of the River Guali and the River Lagunillas, killing 636 people.
•  In 1845, an immense lahar flooded the upper valley of the River Lagunillas, killing over 1000 people.
• It continued for 70 kilometers downstream before spreading across a plain in the lower valley floor.
• The young village of Armero was built directly on top of the 1845 mudflow deposit.
•  Over the ensuing years, Armero grew into a vibrant town with over 27,000 residents.
• On November 13, 1985, history repeated itself for the third time in 400 years, with another eruption and another deadly lahar racing down the River Lagunillas.
•  This time, over 23,000 people were killed, including most of the residents of Armero. With proper planning, this tragedy could have been averted.
• over the last week the volcano has rumbeld back into life as can be seen on the web-Cams on the BBC page : http://www.bbc.co.uk/programmes/p00tmqd6/features/webcams 
• what could this mean for the people who live below the volcano?.. it remains to be seen... however hopefully due to the increase in knowlage of the volcano and increased monitoring the effects will be mitigated and the damages decreased!

Volcano Fact File; Niriagongo

Volcano name- Niriagongo

Volcano type- Strato Volcano

volcano location- DRC

• Mount Nyiragongo is a stratovolcano in the Virunga Mountains associated with the Albertine Rift.

• It is located inside Virunga National Park, in the Democratic Republic of the Congo, about 20 km north of the town of Goma and Lake Kivu and just west of the border with Rwanda.

• The main crater is about two km wide and usually contains a lava lake. The crater presently has two distinct cooled lava benches within the crater walls - one at about 3175m (10,400 ft) and a lower one at about 2975 m (9800 ft).

• Nyiragongo's lava lake has at times been the most voluminous known lava lake in recent history. The depth of the lava lake varies considerably.

• A maximum elevation of the lava lake was recorded at about 3250 m (10,700 ft) prior to the January 1977 eruption - a lake depth of about 600 m (2000 ft).

• A recent very low elevation of the lava lake was recorded at about 2700 m (8800 ft).

• Nyiragongo and nearby Nyamuragira are together responsible for 40% of Africa's historical eruptions

• Not much is known about how long the volcano has been erupting, but since 1882, it has erupted at least 34 times, including many periods where activity was continuous for years at a time, often in the form of a churning lava lake in the crater.

• The volcano partly overlaps with two older volcanoes, Baratu and Shaheru, and is also surrounded by hundreds of small volcanic cinder cones from flank eruptions.

• Volcanism at Nyiragongo is caused by the rifting of the Earth's crust where two parts of the African Plate are breaking apart. A hot spot is probably also partly responsible for the great activity at Nyiragongo and Nyamuragira.

• The lava emitted in eruptions at Nyiragongo is often unusually fluid. Nyiragongo's lavas are made of melilite nephelinite, an alkali-rich type of volcanic rock whose unusual chemical composition may be a factor in the unusual fluidity of the lavas there. Whereas most lava flows move rather slowly and rarely pose a danger to human life,

• Nyiragongo's lava flows may race downhill at up to 60 miles per hour (up to 100 km/h). This is because of the extremely low silica content (the lava is mafic).

• Hawaiian volcanic eruptions are also characterised by lavas with low silica content, but the Hawaiian volcanoes are broad, shallow-sloped shield volcanoes in contrast to the steep-sided cone of Nyiragongo, and the silica content is high enough to slow most Hawaiian flows to walking pace.

• The lava lake activity continued through 2010. At present, the lake is mostly confined within a broad, steep-sided cinder cone on the crater floor, roughly 60 feet high by 600 feet wide.

Volcano Fact file

Volcano Name- Kilauea

Volcano Type- shield volcano


Location- Hawaii


• located in a crater 3,646 ft (1,111 m) deep.


• Kilauea can be found on the Big Island of Hawaii, on the southeastern slope of Mauna Loa, Hawaii Volcanoes National Park.


• Kilauea is one of largest active craters in the world, has a circumference of 8 mi (13 km) and is surrounded by a wall of volcanic rock 200 to 500 ft (61—152 m) high.

• Kilauea is also the youngest volcano in Hawaii. In its floor is Halemaumau, a fiery pit. The usual level of the lake of molten lava is c.740 ft (230 m) below the pit's rim. The oldest dated rock is about 23,000 years old and the oldest eruption of Kilauea was about 300,000-600,000 years ago.


• Kilauea was formed under a hot spot under the crust. So were the other volcanoes on the Big Island such as Kohala, Mauna Kea, Mauna Loa, and Hualalai.


• There have been 34 eruptions since 1952 and 61 eruptions total. In early 1973, an earthquake occurred that caused Kilauea to stop erupting and instead erupt near the craters Pauahi and Hi'iaka.


• Current eruption began January 3, 1983 and is called Pu'u'O'o.

• Hawaii, nicknamed BIG ISLAND because of it's 8 major volcanoes, is currently 4038 square miles (approx. 6 500 square km ) and grows around 42 acres every year thanks to all of mount Kilauea's eruptions.


• Mount Kilauea is one of 5 active volcanoes in Hawaii, others are Loihi, Mauna Loa, Hualalai and Haleakala.


• Mount Kilauea Volcano is home of Fire Goddess, Pele.

link!

http://www.bbc.co.uk/programmes/p00tmqdr/features/livechat

VOLCANOES!

Well inspired by this weeks BBC program Volcano Live... i am going to start profiling the various volcanoes mentioned on the program!

The Dead Sea

well... during a quick break from revision heres another post... this time on the Dead Sea

The Dead sea

The Dead sea is one of the most geologically fascinating places on the planet.

The Dead Sea is an endorheic lake located in the Jordan Rift Valley, a geographic feature formed by the Dead Sea Transform (DST). This left lateral-moving transform fault lies along the tectonic plate boundary between the African Plate and the Arabian Plate. It runs between the East Anatolian Fault zone in Turkey and the northern end of the Red Sea Rift offshore of the southern tip of Sinai.

 

The Jordan River is the only major water source flowing into the Dead Sea, although there are small perennial springs under and around the Dead Sea, creating pools and quicksand pits along the edges. There are no outlet streams.

Rainfall is scarcely 100 mm (4 in) per year in the northern part of the Dead Sea and barely 50 mm (2 in) in the southern part. The Dead Sea zone's aridity is due to the rainshadow effect of the Judean Hills. The highlands east of the Dead Sea receive more rainfall than the Dead Sea itself.

To the west of the Dead Sea, the Judean Hills rise less steeply and are much lower than the mountains to the east. Along the southwestern side of the lake is a 210 m (700 ft) tall halite formation called "Mount Sodom".

There are two contending hypotheses about the origin of the low elevation of the Dead Sea. The older hypothesis is that it lies in a true rift zone, an extension of the Red Sea Rift, or even of the Great Rift Valley of eastern Africa. A more recent hypothesis is that the Dead Sea basin is a consequence of a "step-over" discontinuity along the Dead Sea Transform, creating an extension of the crust with consequent subsidence.

Around three million years ago what is now the valley of the Jordan River, Dead Sea, and Wadi Arabah was repeatedly inundated by waters from the Mediterranean Sea. The waters formed in a narrow, crooked bay which was connected to the sea through what is now the Jezreel Valley. The floods of the valley came and went depending on long scale climate change. The lake that occupied the Dead Sea Rift, named "Lake Sedom", deposited beds of salt that eventually became 3 km (2 mi) thick

Approximately two million years ago, the land between the Rift Valley and the Mediterranean Sea rose to such an extent that the ocean could no longer flood the area. Thus, the long bay became a lake.

The first such prehistoric lake is named "Lake Amora". Lake Amora was a freshwater or brackish lake that extended at least 80 km (50 mi) south of the current southern end of the Dead Sea and 100 km (60 mi) north, well above the present Hula Depression. As the climate became more arid, Lake Amora shrank and became saltier. The large, saltwater predecessor of the Dead Sea is called "Lake Lisan."

In prehistoric times, great amounts of sediment collected on the floor of Lake Amora. The sediment was heavier than the salt deposits and squeezed the salt deposits upwards into what are now the Lisan Peninsula and Mount Sodom (on the southwest side of the lake). Geologists explain the effect in terms of a bucket of mud into which a large flat stone is placed, forcing the mud to creep up the sides of the pail. When the floor of the Dead Sea dropped further due to tectonic forces, the salt mounts of Lisan and Mount Sodom stayed in place as high cliffs. (see salt domes)

From 70,000 to 12,000 years ago, the lake level was 100 m (330 ft) to 250 m (820 ft) higher than its current level. This lake, called "Lake Lisan", fluctuated dramatically, rising to its highest level around 26,000 years ago, indicating a very wet climate in the Near East. Around 10,000 years ago, the lake level dropped dramatically, probably to levels even lower than today. During the last several thousand years, the lake has fluctuated approximately 400 m (1,300 ft), with some significant drops and rises. Current theories as to the cause of this dramatic drop in levels rule out volcanic activity; therefore, it may have been a seismic event.

this has to be one of the most fascinating pieces of geology i have come accross in the past two years. not only geologically fascinating but also beautiful...

Dallol

Dallol.....


Dallol is an interesting volcano in Ethiopia.


It was shown on the program “ The Hottest Place on earth”

It is an explosion crater in the Danakill depression- northeast of Erta Ale. It has been formed by the intrusion of basaltic magma into the Miocene salt deposits and the subsequent hydrothermal activity.

Phreatic eruptions-

(also known as ultravulcanian eruptions occurs when magma heats ground or surface water- the temperature of the magma causes near instantaneous evaporation to steam that results in an explosion of steam, water, ash, rock, and volcanic bombs)

These occurred in 1926- this formed the crater and the crater and the other craters that dot the nearby salt flats,

Numerous hot springs are discharging brine and acidic liquid here. Widespread are small, temporary geysers which are forming cones of salt.

The term Dallol was coined by the Afar people and means dissolution or disintegration describing a landscape made up of green acid ponds (pH-values less than 1) iron oxide, sulfur and salt desert plains. The area resembles the hot springs areas of Yellowstone Park.

Sorry about the length of this post but it is a stop gap while I work on a longer more interesting one!!

The Eye Of The Sahara

Eye of the Sahara (Mauritania)The eye is located in central Mauritania near Ouadane. This structure is a deeply eroded, slightly elliptical, 40-km in diameter, dome. The sedimentary rock exposed in this dome range in age from Late Proterozoic within the center of the dome to Ordovician sandstone around its edges. The sedimentary rocks comprising this structure dip outward at 10°-20°.

Differential erosion of resistant layers of quartzite has created high-relief circular cuestas. Its center consists of a siliceous breccia covering an area that is at least 3 km in diameter.

Exposed within the interior of the Richat structure are a variety of intrusive and extrusive igneous rocks. They include Rhyolitic volcanic rocks, gabbros, carbonatites and kimberlites. The Rhyolitic rocks consist of lava flows and hydrothermally altered tuffaceous rocks that are part of two distinct two eruptive centers, which are interpreted to be the eroded remains of two maars.

According to field mapping and aeromagnetic data, the gabbroic rocks form two concentric ring dikes. The inner ring dike is about 20 m in width and lies about 3 km from the center of Richat Structure. The outer ring dike is about 50 m in width and lies about 7 to 8 km from the center of this structure.

Thirty-two carbonatite dikes and sills have been mapped within the Richat structure. The dikes are generally about 300 m long and typically 1 to 4 m wide. They consist of massive carbonatites that are mostly devoid of vesicles. The carbonatite rocks have been dated as having cooled between 94 to 104 million years ago.

A kimberlitic plug and several sills have been found within the northern part of the Richat structure. The kimberlite plug has been dated being about 99 million years old. These intrusive igneous rocks are interpreted as indicating the presence of a large alkaline igneous intrusion that currently underlies the Richat structure and created it by uplifting the overlying rock.
Spectacular hydrothermal features are a part of the Richat structure. They include the extensive hydrothermal alteration of rhyolites and gabbros and a central megabreccia created by hydrothermal dissolution and collapse.

The siliceous megabreccia is at least 40 m thick in its center to only a few meters thick along its edges. The breccia consists of fragments of white to dark gray cherty material, quartz-rich sandstone, diagenetic cherty nodules, and stromatolitic limestone and is intensively silicified. The hydrothermal alteration, which created this breccia, has been dated to have occurred about 98.2 ± 2.6 million years ago using the 40 Ar/ 39 Ar method.

Initially interpreted as an asteroid impact structure because of its high degree of circularity, it is now argued to be a highly symmetrical and deeply eroded geologic dome. Despite extensive field and laboratory studies, geologists have found a lack of any credible evidence forshock metamorphisam any type of deformation indicative of a hypervelocity extraterrestrial impact.
coesite, an indicator of shock metamorphism, had been reported as being present in rocks samples collected from the Richat structure.

As the result of the further analysis of rock samples from this structure, it was concluded that barite had been misidentified as coesite.
In addition, the Richat structure lacks the annular depression that characterizes large extraterrestrial impact structures of this size. Also, it is quite different from large extraterrestrial impact structures in that the sedimentary strata comprising this structure is remarkably intact and "orderly" and lacking in overturned, steeply-dipping strata or disoriented blocks.

A more recent multianalytical study on the Richat mega breccias concluded that carbonates within the silica-rich mega breccias were created by low-temperature hydrothermal waters, and that the structure requires special protection and further investigation of its origin.

The Cave Of Crystals

The Cave of Crystals

The cave of crystals or Cueva de los Cristales- is an amazing geological formation in Mexico.

This is a cave connected to the Naica mine that sits 300m below the surface.

The main chamber contains giant gypsum crystals.


The largest crystal that has been found to date is 11 m in length and weighs 55 tonnes.


The cave is really hot with 90-99% humidity and it is due to these factors that the cave is as of yet realtivly unexplored as without the proper protection people can only have 10 minutes exposure at any one time.


Formation of the crystals


Naica lies on an ancient fault and there is an underground magma chamber below the cave. The magma heated the ground water and it became saturated with minerals, including large quantities of gypsum. The hollow space of the cave was filled with this mineral-rich hot water and remained filled for about 500,000 years. During this time, the temperature of the water remained very stable at over 50 °C. This allowed crystals to form and grow to immense sizes

 Discovery

In 1910 miners discovered a cavern beneath the Naica mine workings, the Cave of Swords (Spanish: Cueva de las Espadas). It is located at a depth of 120 m, above the Cave of Crystals, and contains spectacular, smaller (1 m long) crystals. It is speculated that at this level, transition temperatures may have fallen much more rapidly, leading to an end in the growth of the crystals.

The Giant Crystal cave was discovered in 2000 by miners excavating a new tunnel for the Industrias Peñoles mining company located in Naica, Mexico, while drilling through the Naica fault, which they were concerned would flood the mine. The mining complex in Naica contains substantial deposits of silver, zinc and lead.

The Cave of Crystals is a horseshoe-shaped cavity in limestone rock. Its floor is covered with perfectly-faceted crystalline blocks. Huge crystal beams jut out from both the blocks and the floor. The caves are accessible today because the mining company's pumping operations keep them clear of water. If the pumping were stopped, the caves would again be submerged. The crystals deteriorate in air, so the Naica Project is attempting to visually document the crystals before they deteriorate further.

A further chamber was found in a drilling project in 2009. The new cave, named the Ice Palace, is 150 m deep and is not flooded, but its crystal formations are much smaller, with small 'cauliflower' formations and fine, threadlike crystals

Exploration hinted at the existence of further chambers, but further exploration would have required demolition of the crystals. It was stated that the cave would eventually be resealed and the water level allowed to rise again.

Ol Doinyo Lengai

Ol Doinyo Lengai is an active volcano located in the north of Tanzania and is part of the volcanic system of the East African Rift. It is located in the eastern Rift Valley, or Gregory Rift, south of both Lake Natron and Kenya. It is unique among active volcanoes in that it produces natrocarbonatite lava, a unique occurrence of volcanic carbonatite. Further, the temperature of its lava as it emerges is only around 510 °C (950 °F). A few older extinct carbonatite volcanoes are located nearby, including Homa Mountain.

Ol Doinyo Lengai" means "The Mountain of God" in the Maasai language of the native people. The record of eruptions on the mountain dates to 1883, and flows were also recorded between 1904 and 1910 and again between 1913 and 1915. A major eruption took place in June 1917, which resulted in volcanic ash being deposited about 48 kilometers away.

A similar eruption took place for several months in 1926 and between July and December 1940, resulting in the ash being deposited as far as Loliondo, which is 100 kilometres away. Several minor eruptions of lava were observed in 1954, 1955, 1958 the early 1960s.

When Ol Doinyo Lengai erupted on August 14, 1966, two geologists — J. B. Dawson and G. C. Clark — who visited the crater a week later, reported seeing “a thick column of black ash” that rose for approximately three thousand feet above the volcano and drifted away northwards towards Lake Natron. When the two climbed the cone-shaped vent, they reported seeing a continuous discharge of gas and whitish-grey ash and dust from the centre of the pit.

Volcanic activity in the mountain caused daily earth tremors in Kenya and Tanzania beginning on July 12, 2007. The latest to hit parts of Nairobi city was recorded on July 18, 2007 at 8.30pm (Kenyan Time). The strongest tremor measured 6.0 on the Richter scale. Geologists suspected that the sudden increase of tremors was indicative of the movement of magma through the Ol Doinyo Lengai. The volcano finally erupted on September 4, 2007, sending a plume of ash and steam at least 18 kilometers downwind and covering the north and west flanks in fresh lava flows. The eruption has continued intermittently into 2008, as of the end of February it was reported that the eruption appeared to be gathering strength, with a major outburst taking place on March 5. During April periods of inactivity have been followed by eruptions on April 8 and 17. Eruptive activity continued until late August 2008. A visit to the summit in September 2008 discovered that lava emission had resumed from two vents in the floor of the new crater. Visits to the crater in March/April 2009 showed that even this activity appears to have ceased

Whereas most lavas are rich in silicate minerals, the lava of Ol Doinyo Lengai is a carbonatite. It is rich in the rare sodium and potassium carbonates, nyerereite and gregoryite. Due to this unusual composition, the lava erupts at relatively low temperatures of approximately 500-600 degrees Celsius. This temperature is so low that the molten lava appears black in sunlight, rather than having the red glow common to most lavas. It is also much more fluid than silicate lavas, often less viscous than water. The sodium and potassium carbonate minerals of the lavas formed by Ol Doinyo Lengai are unstable at the Earth's surface and susceptible to rapid weathering, quickly turning from black to grey in color. The resulting volcanic landscape is different from any other in the world.

The rift Valley

The rift valley – also known as the Great Rift Valley or the East African rift.

Basic Information.

The East African Rift is an active continental rift zone in eastern Africa that appears to be a developing divergent tectonic plate boundary. In the past it was considered to be part of a larger Great Rift Valley that extended north to Turkey. The rift is a narrow zone in which the African Plate is in the process of splitting into two new tectonic plates called the Somali Plate and the Nubian Plate, which are sub plates or protoplates.

The East African Rift runs from the Afar Triple Junction in the Afar Depression southward through eastern Africa. It is believed to run offshore of the coast of Mozambique along the Karimba and Lacerda rifts or grabens, terminating in the Andrew Bain Fracture Zone complex, where it is believed to have its junction with the Southwest Indian Ridge.

In simple terms, a rift can be thought of as a fracture in the earth's surface that widens over time, or more technically, as an elongate basin bounded by opposed steeply dipping normal faults. Geologists are still debating exactly how rifting comes about, but the process is so well displayed in East Africa (Ethiopia-Kenya-Uganda-Tanzania) that geologists have attached a name to the new plate-to-be; the Nubian Plate makes up most of Africa, while the smaller plate that is pulling away has been named the Somalian Plate. These two plates are moving away from each other and also away from the Arabian plate to the north. The point where these three plates meet in the Afar region of Ethiopia forms what is called a triple-junction. However, all the rifting in East Africa is not confined to the Horn of Africa; there is a lot of rifting activity further south as well, extending into Kenya and Tanzania and Great Lakes region of Africa. The purpose of this paper is to discuss the general geology of these rifts are and highlight the geologic processes involved in their formation.

The East African Rift consists of two main branches called the Gregory Rift and the Western Rift Valley. These result from the actions of numerous normal (dip-slip) faults which are typical of all tectonic rift zones. The Eastern Rift Valley includes the Main Ethiopian Rift, running eastward from the Afar Triple Junction, which continues south as the Kenyan Rift Valley. The Western Rift Valley includes the Albertine Rift, and further south the valley of Lake Malawi.

The East African Rift Zone includes a number of active as well as dormant volcanoes. These include Mount Kilimanjaro, Mount Kenya, Mount Longonot, Menengai Crater, Mount Karisimbi, Mount Nyiragongo, Mount Meru and Mount Elgon as well as the Crater Highlands in Tanzania. The Ol Doinyo Lengai volcano remains active, and is currently the only natro-carbonatite volcano in the world. Erta Ale is a continuously active basaltic shield volcano in the Afar Region of northeastern Ethiopia.

Formation.

The exact mechanism of rift formation is an on-going debate among geologists and geophysicists. One popular model for the EARS assumes that elevated heat flow from the mantle (strictly the asthenosphere) is causing a pair of thermal "bulges" in central Kenya and the Afar region of north-central Ethiopia. These bulges can be easily seen as elevated highlands on any topographic map of the area (Figure 1). As these bulges form, they stretch and fracture the outer brittle crust into a series of normal faults forming the classic horst and graben structure of rift valleys. Most current geological thinking holds that bulges are initiated by mantle plumes under the continent heating the overlying crust and causing it to expand and fracture. Ideally the dominant fractures created occur in a pattern consisting of three fractures or fracture zones radiating from a point with an angular separation of 120 degrees. The point from which the three branches radiate is called a "triple junction" and is well illustrated in the Afar region of Ethiopia where two branches are occupied by the Red Sea and Gulf of Aden, and the third rift branch runs to the south through Ethiopia.

The stretching process associated with rift formation is often preceded by huge volcanic eruptions which flow over large areas and are usually preserved/exposed on the flanks of the rift. These eruptions are considered by some geologists to be "flood basalts" - the lava is erupted along fractures (rather than at individual volcanoes) and runs over the land in sheets like water during a flood. Such eruptions can cover massive areas of land and develop enormous thicknesses (the Deccan Traps of India and the Siberian Traps are examples). If the stretching of the crust continues, it forms a "stretched zone" of thinned crust consisting of a mix of basaltic and continental rocks which eventually drops below sea level, as has happened in the Red Sea and Gulf of Aden. Further stretching leads to the formation of oceanic crust and the birth of a new ocean basin.

If the rifting process described occurs in a continental setting, then we have a situation similar to what is now occurring in Kenya where the East African/Gregory Rift is forming. In this case it is referred to as "continental rifting" (for obvious reasons) and provides a glimpse into what may have been the early development of the Ethiopian Rift.

the rifting of East Africa is complicated by the fact that two branches have developed, one to the west which hosts the African Great Lakes (where the rift filled with water) and another nearly parallel rift about 600 kilometres to the east which nearly bisects Kenya north-to-south before entering Tanzania where it seems to die out . Lake Victoria sits between these two branches. It is thought that these rifts are generally following old sutures between ancient continental masses that collided billions of years ago to form the African craton and that the split around the Lake Victoria region occurred due to the presence of a small core of ancient metamorphic rock, the Tanzania craton, that was too hard for the rift to tear through. Because the rift could not go straight through this area, it instead diverged around it leading to the two branches that can be seen today.

As is the case in Ethiopia, a hot spot seems to be situated under central Kenya, as evidenced by the elevated topographic dome there. This is almost exactly analogous to the rift Ethiopia, and in fact, some geologists have suggested that the Kenya dome is the same hotspot or plume that gave rise to the initial Ethiopian rifting. Whatever the cause, it is clear that we have two rifts that are separated enough to justify giving them different names, but near enough to suggest that they are genetically related.

In conclusion the rift valley is spreading and will eventually split apart completely forming the Nubian and Somalian plate.

Update!!!!- 18/02/2016
so- as the rift valley is one of my favorite things!!!

I have recently become involved with a project- GeomissionUganda that seeks to help establish sustainable geological tourism on the east Albertine rift- part of the Rift valley! we aim to set up a route that encorperates much of the amazing geology that Ugnada's Albertine rift offers as well as teaching about it and trainging rangers in both the uk and Ugnada, how to make the most of what this beautiful country has to offer!  We will be traveling there in September to start getting things done in order for the main trip in 2017! However to do this we need to raise funding which is where our crowdfunding campaign comes in!So please take a look and hopefully fund us! For more information see the blog post I put up yesterday!!! 

Cheers

AJ