This is the third cache in the wide area of Tsavo West.
You are standing in an relatively young lava flow.
Tsavo West is marked by a number of recent rocky outcrops and volcanic hills.
The youngest being only a few hundred years old. Breaking out of the Precambrian basement system, these volcanos first appeared in the Pleistocene epoch, between 1,8 million and a mere 10000 years ago.
The parks two most attractive scenic features (besides MZIMA SPRINGS), rose from volcanic activity: Chyulu Hills in the northwest and the YATTA Plateau along the east side of the Athi River.
The Chyulu Hills (north of you) consist of a series of volcanoes , many of which are largely composed of volcanic ash cones.
The Chyulu Hills were created by volcanic activities/action which was very recent in geological history. The estimations differ to be in any case less than 500 years, but some claim it to be around 200 years. This makes them one of the world’s youngest mountain ranges.
I might set up another earth cache here: Deep beneath the hills is a catacomb of caves, most of them still unexplored. In 1975 the Cave Exploration Group of East Africa discovered one cave that was 13 km long and in some places as wide as half a kilometer. It was named Leviathan and turned out to be the second largest lava cave in the world.
This cave can be visited (you might see some signs when approaching ground zero from the park side), but only under the guidance of a park ranger.
Shetani is a volcano that stands about half-way up the southern end of Chyulu range. It is a small volcano which became extinct, or perhaps only dormant, such a short time ago that it still retains, in a perfectly fresh condition, very many of the most interesting characteristics of a volcano. It needs exceedingly little imagination to picture it in eruption. It is a black lava cone, about 450feet above the immediate surrounding and it carries many legends and stories from the past. Shetani means devil, and the local people believe it is haunted. It is claimed that anyone attempting to climb this volcano will hear screams, dogs waiting and chickens crowing, but will never return. If one approaches the cone too closely, a strong age to climb it up to the top is felt, but if one does, he will never return. The second warden of Tsavo West, T. Marshall, wrote m a letter in 1952: "The guide who came with us was ranger Nduma, son of Nguli; he is an ex poacher who was born at Ngulia, where we now have our lodge. Nduma says that his father could remember when a red glow could always be seen on the top of Shetani after dark (this could be around 80 to 90 years ago) and that game and honey hunters who went anywhere near the hill were never seen again." (This might have been possibly due to Sulphur fumes).
Col. Mervyn Cowie, first Director of the National Parks, informed the Tsavo West park personnel that he had spoken to veterans of the 1914-1919 War who went through the East African Campaign. They told him that Shanti was used by the British as a look-on station. It was later suggested that the stories of crowing cockerels, barking dogs and mowing cattle might be due to sounds made by high winds rushing through the lava fields or across the crater's mouth.
It is however, one of the most interesting lava formations in the area, as it is a perfect example of a recent volcano. The volcano itself is only approached on foot and by permission of, and arrangement with, the Warden. Here there are also three craters resulting from a movement of the center of the volcano during eruptions.
But you are relatively safe, standing in the mid of the relative young lava stream. You can as well see, how nature is trying to grow one some spots again.
Lava is molten rock generated by geothermal energy and expelled through fractures in planetary crust or in an eruption, usually at temperatures from 700 to 1,200 °C (1,292 to 2,192 °F). The resulting structures after solidification and cooling are also sometimes described as lava. The molten rock is formed in the interior of some planets, including Earth, and some of their satellites, though such material located below the crust is referred to by other terms. A lava flow is a moving outpouring of lava created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock. The term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic and shear thinning properties. The sub-family of rocks that form from volcanic lava are called igneous volcanic rocks. The lavas of different volcanoes, when cooled and hardened, differ much in their appearance and composition. If a rhyolite lava-stream cools quickly, it can quickly freeze into a black glassy substance called obsidian. When filled with bubbles of gas, the same lava may form the spongy appearing pumice. Allowed to cool slowly, it forms a light-colored, uniformly solid rock called rhyolite. The lavas, having cooled rapidly in contact with the air or water, are mostly finely crystalline or have at least fine-grained ground-mass representing that part of the viscous semi-crystalline lava flow that was still liquid at the moment of eruption. At this time they were exposed only to atmospheric pressure, and the steam and other gases, which they contained in great quantity were free to escape; many important modifications arise from this, the most striking being the frequent presence of numerous steam cavities (vesicular structure) often drawn out to elongated shapes subsequently filled up with minerals by infiltration. As crystallization was going on while the mass was still creeping forward under the surface of the Earth, the latest formed minerals (in the ground-mass) are commonly arranged in subparallel winding lines that follow the direction of movement (fluxion or fluidal structure)—and larger early minerals that previously crystallized may show the same arrangement. Most lavas fall considerably below their original temperatures before emitted. In their behavior, they present a close analogy to hot solutions of salts in water, which, when they approach the saturation temperature, first deposit a crop of large, well-formed crystals (labile stage) and subsequently precipitate clouds of smaller less perfect crystalline particles (metastable stage). In igneous rocks the first generation of crystals generally forms before the lava has emerged to the surface, that is to say, during the ascent from the subterranean depths to the crater of the volcano. It has frequently been verified by observation that freshly emitted lavas contain large crystals borne along in a molten, liquid mass. The large, well-formed, early crystals (phenocrysts) are said to be porphyritic; the smaller crystals of the surrounding matrix or ground-mass belong to the post-effusion stage. More rarely lavas are completely fused at the moment of ejection; they may then cool to form a non-porphyritic, finely crystalline rock, or if more rapidly chilled may in large part be non-crystalline or glassy (vitreous rocks such as obsidian, tachylyte, pitchstone). A common feature of glassy rocks is the presence of rounded bodies (spherulites), consisting of fine divergent fibres radiating from a center; they consist of imperfect crystals of feldspar, mixed with quartz or tridymite; similar bodies are often produced artificially in glasses that are allowed to cool slowly. Rarely these spherulites are hollow or consist of concentric shells with spaces between (lithophysae). Perlitic structure, also common in glasses, consists of the presence of concentric rounded cracks owing to contraction on cooling. The phenocrysts or porphyritic minerals are not only larger than those of the ground-mass; as the matrix was still liquid when they formed they were free to take perfect crystalline shapes, without interference by the pressure of adjacent crystals. They seem to have grown rapidly, as they are often filled with enclosures of glassy or finely crystalline material like that of the ground-mass . Microscopic examination of the phenocrysts often reveals that they have had a complex history. Very frequently they show layers of different composition, indicated by variations in color or other optical properties; thus augite may be green in the center surrounded by various shades of brown; or they may be pale green centrally and darker green with strong pleochroism (aegirine) at the periphery. In the feldspars the center is usually richer in calcium than the surrounding layers, and successive zones may often be noted, each less calcic than those within it. Phenocrysts of quartz (and of other minerals), instead of sharp, perfect crystalline faces, may show rounded corroded surfaces, with the points blunted and irregular tongue-like projections of the matrix into the substance of the crystal. It is clear that after the mineral had crystallized it was partly again dissolved or corroded at some period before the matrix solidified.
Please take care at cache site: walking in lava rocks poses some dangers for your skin, ankles etc.!
Questions to be kindly answered before logging this cache (logs without answers and log permission will be deleted):
1) Ground Zero: What is the last line in the large sign (on the biggest rock you can find here, you can’t miss it). Please give it in the exact writing and with all punctuations.
2) What do you find at the ‘extra stage”. If you are coming from the caches coordinates on the left hand side of the street. How deep is it? Describe the formation (under street level). What do you think do you see here?
3) Why do you think the Chyulu Hills act as a water reservoir? Which feature of the rocks helps? If you are in doubt: compare the weight of one of the smaller rocks with other stones you know.
4) Mzima Springs is another nice spot situated 48 km from Mtitu Andei. It is located in the vast and semi dry wilderness of Tsavo – West. It looks almost (if you don’t come in rainy season when all Tsavo is green like I found it in March 2018) like a desert oasis. Mzima Springs plays a vital role as the source of water for Mombasa and other towns en-route. Connected by a pipeline completed in 1966 to Mombasa.
Can you explain why the water in Mzima Springs is so clear and where it is coming from?
5) (of course optional) Please post a pic of you/your GPS/ with area.
Many of the above mentioned information on the special area are from Severin Tsavo Lodge’s ‘Tsavo Book’. The one titled ‘nature and landscapes’.
Some information on lava is from Wikipedia as well