HELL'S GATE GORGE - OL NJOROWA GORGE EarthCache

To get to this Earthcache, you will have visit Hell’s Gate National Park in Kenya. To log this cache, you must travel to the given coordinates and answer the geological questions. Permission to visit this area is granted by the Park Rangers who are employed by the National Park and are stationed at the coordinates given for parking below. A guide is recommended.

This is the trailhead and entrance to the lower gorge. A guide is highly recommended even if there is no indication of rain/flash floods. It will make for an amazing experience; a 2 hour expedition of geological experience of beauty and function, water eroded walls so narrow that they almost block out the sky, several hot and cold waterfalls, hot water springs, and colorful strata and rock formations.

Hell's Gate National Park is a park located between Lake Naivasha and the Longonot and Suswa volcanoes. It is covered by ashes from the Longonot eruption which occurred 100 years ago, the park is famous for its geothermal station, the Lower Gorge- “Ol Njorwa’s Gorge”, and spectacular sceneries (cliffs, volcanoes gorges, and geothermal steam).

The on-going geological processes at Hell's gate are similar to the processes at Lake Bogoria national reserve in Kenya, these has made the sites exceptionally beautiful and unique.

The Olkaria and Hobley's, two extinct volcanoes located in the park, can be seen as well as obsidian forms from the cool molten lava. Park has varied landscapes with red rock cliffs and Volcanic plugs: Fischer's Tower and Central Tower which are very popular with both amateur and professional climbers.

'Gorge' is the French word for throat or neck. They are often referred to as canyons, ravines, or valleys but these alternate names, however, are not the equivalent landform of a gorge. A gorge is typically any narrow or deep valley between tall slabs of steep rock on either side and has a source of water flowing through the bottom of the valley.

As stated above a gorge is a narrow valley or ravine between two rocky walls that are usually mountains or hills. There is usually a river or some stream of water that flows down the middle at the bottom of the valley. Gorges, valleys, and canyons can be quite similar but their characteristics, composition, the ways in which they are created and where (the regions) make the difference in name. For example gorges are typically smaller in size, far more narrow, and much steeper than canyons. As well, canyons do not always have to have a stream of water moving across the bottom of the ravine as gorges usually do.

Gorges are the result of erosion and geological uplift over long periods of time. When streams or rivers flow through mountains, they break away and wear down the rock, also tearing away sediments of rock. In other words, moving sources of water are able to erode the rock until it becomes the steep and narrow walls of a gorge. Interestingly, lava flow can also create gorges much like water does! Geological uplift is defined as the vertical elevation of the Earth's crust or surface. This could be the movement of crusts rising over or under each other (forming mountains) or it could be the natural force of fault lines that cause collisions of crusts, resulting in a vertical elevation or uplift of the Earth's surface. This uplifting of land allows for the water to be lifted as well and continue eroding the rock away from a mountain. Moreover, as the water continues to flow over the uplift, it forms a waterfall. With the speed and power of the waterfall breaking down the rock continually and consistently, eventually the softer layers of rock collapse, forming a gorge. A less common method of the formation of gorges is through glaciers and glacier movement. When glaciers scrape across the Earth, they can create deep valleys in the surface and thus forming a narrow and sharp gorge.

Gorges are often found with other sensational landforms around it and are often classified with many similar landforms as well. Gorges usually appear in mountainous areas and they are typically found as a ravine or very steep valley between two mountains. They are also associated with hills because it is not uncommon for gorges to be cut from hills lush with forests. Usually, a river or stream flows down the middle at the bottom of the gorge and it would move downstream. Also, most gorges are made up of granite, sandstone, and limestone in composition. Sometimes, fossils can be found buried in the layers of rock that hold the walls of the gorge. They are also found everywhere on the planet, so long as there are mountain ranges or hills. In addition, they can appear in almost any climate, from areas where volcanoes are active to regions where the temperature allows for glaciers to be present all-year round.

The layers of rock inside gorges are estimated to be around 2 million years old, formed during the Cenozoic era. However, the cutting of gorges with rivers and channels of water is estimated to have taken anywhere from 3 million to 320 million years (between the Cenozoic and the Paleozoic era), depending on the gorge and its location.

Gorges can be found almost anywhere in the world, so long as that region or area contains uplifted land of hills or mountains. Where there are fault lines and movement of the crust, there are mountains or some type of vertical elevation of the Earth's surface. In these places, with the combination of a channel (or body) of water that is dynamic, there are likely formations of gorges. Across the globe, there are examples of different gorges and their physical locations truly represent the varying places and regions in which they are found!

THE OLNJOROWA GORGE

The scenic Olnjorowa Gorge was formed by erosion of Lake Naivasha when it breached on the southern side and the Lower Gorge.

Lake Naivasha in the ancient days used to be a massive giant lake lying on the floor of the Rift Valley. The Lake used to collect its water from different catchment areas like the Mau escarpment and the Aberdare ranges. Lake Enaiposha (present Lake Naivasha) had an outlet flowing through Hell’s gate gorge and in the process cutting and eroding as well as depositing for hundred of thousand years. The Maasai used to call this outlet as river Ol-Njorowa. Lake Enaiposha used to extend as far as Lake Baringo. After the eruption of Mt Longonot, Mt Suswa and Menengai, the volume of the lake was reduced gradually as a result of the very hot volcanic ashes into and around the lake, thus sub-dividing the lake into two different types of lakes i.e. the fresh water lakes and the salty lakes. The fresh water lakes are Lake Enaioposha (Naivasha) and Lake Baringo while the salty lakes are Nakuru, Bogoria and Elementaita. Initially all these lakes are believed to have been one massive Lake Enaiposha. The small Lake Naivasha has no more main outlet apart from the underground ones, one such outlet is said to drain to Ondiri swamp in Kikuyu. The Ol-Njorowa River dried when water from the Lake Naivasha stopped flowing through the gorge.

Ol-Njorowa river is now fed by the cold and the hot springs either on the floor of the gorge or the sides, it therefore reduced into a small steam running from the starting point of the gorge downwards to the paramount tower after then, it dries up as it goes underground and by the end, the gorge opens up into a plain known as the Suswa plains.

Hell's gate represents an area of great geological phenomenon (i.e. hot water geysers and hot springs) these land formations and on-going geological processes at Hell's gate make the area exceptionally beautiful and unique compared to any other area. Presence of vegetation around the hot water is remarkable as these plants are able to survive in very high temperatures.

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Ref: http://whc.unesco.org/en/tentativelists/5511/