Travels in Geology: Tanzania's natural wonders

Ngorongoro Crater, part of the Ngorongoro Conservation Area, which also includes Olduvai Gorge, Ol Doinyo Lengai and abundant wildlife.

Africa's highest peak is Kibo, at the summit of Mount Kilimanjaro in Tanzania.

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Ol Doinyo Lengai, the "Mountain of God," erupts carbonatite lava rich in sodium and potassium carbonate minerals.

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Plains zebra and blue wildebeests in Ngorongoro Crater in Tanzania's Serengeti Plains.

Olduvai Gorge, the "Cradle of Mankind," in the Serengeti Plains of northern Tanzania. Olduvai contains artifacts of human ancestors that are as old as 2.5 million years.

Karst caves on the island of Zanzibar, including Mangapwani Coral Cavern, were used in the latter part of the 19th century to hide slaves after the slave trade was abolished in 1873.

Eco-bungalows on Chumbe Island.

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Guido Cozzi

Tanzania's natural wonders — towering volcanoes, paradisaical islands and sundry animal life — have inspired travelers from Ernest Hemingway (who hunted big game) to the rock band Toto (who rhymed “Serengeti” with “company”). Situated on Africa’s eastern coast, Tanzania consists of the mainland country, once called Tanganyika, and the exotic archipelago Zanzibar, located in the Indian Ocean 25 to 50 kilometers from the mainland.

It may be hard to believe that the sleepy, benign mountains that reign over the plains are capable of violent eruption, but Tanzania is home to many volcanoes and volcanic features. The iconic Mount Kilimanjaro is located in northeastern Tanzania and boasts the highest peak on the continent, Kibo, at 5,892 meters. Kilimanjaro actually consists of three concentric volcanoes that formed less than a million years ago as a result of the same seismic activity that is forming the African Rift Valley to the north, where Earth’s crust is slowly pulling apart and magma is rising to the surface.

For the ambitious hiker, Kilimanjaro presents a stunning array of both ecological and geological features. It is one of the largest stratovolcanoes on Earth, which means that at its lower reaches, it slopes at very low angles, making ascending the mountain not quite as grueling and adding to its reputation as one of the easiest of the so-called Seven Summits, the highest peaks on each continent.

Because of its height and near-equatorial latitude, Kilimanjaro displays almost every ecological zone from its base to its peak, including glaciers that cover its summit year-round. Kilimanjaro has not erupted in recorded history, but the summit crater hosts active fumaroles, which emit steam as well as sulfur. To make this challenging climb, hikers can choose from several walking paths, some more difficult than others, that lead to different summits. Using a guide is a must if you want to make this difficult climb, and the cost of this 7- to 10-day trek averages around several thousand dollars per person. Even if you don’t choose to make the challenging climb, Kilimanjaro is a must-see site if you visit Tanzania.

Kilimanjaro is only one of many volcanoes, some extinct and some active, that are part of the Rift Valley system. Ngorongoro Crater, in the Ngorongoro Conservation Area west of Kilimanjaro, is the caldera of a now-extinct volcano. It is the largest unbroken caldera in the world and hosts many different ecological areas, boasting the densest concentration of wildlife on the planet. Inside the crater, between 20,000 and 30,000 wild animals stalk at any one time, including the endangered black rhino. The surrounding Ngorongoro Conservation Area protects more than 8,000 square kilometers of the wilderness. At the luxurious Ngorongoro Crater Lodge, you can have the unique experience of dining on the edge of the crater, complete with spectacular views of the crater’s interior as well as the surrounding area. Within the Ngorongoro Conservation Area are four other calderas, the Olmoti Crater (great for safaris on foot), the Empakaai Crater (the soda lake that covers half the crater floor is home to a wide variety of bird life), and the Ol Donyo Lengai Crater. Each crater is unique and boasts a different set of wildlife or geology, making each one worth a visit.

But some of Tanzania’s volcanoes are still extremely active, and violently so. Ol Doinyo Lengai ("Mountain of God" in the language of the native Maasai people), about 80 kilometers from Ngorongoro Crater, is also within the conservation area. The volcano has had a series of constant eruptions since the mid-1980s, the most recent of which ended only last year. The reason behind these frequent eruptions is that Ol Doinyo Lengai erupts rare natrocarbonatite lava, rich in sodium and potassium carbonate minerals, which allows lava to erupt at a lower temperature than typical silicic lava. Although Ol Doinyo Lengai is steeper than Kilimanjaro, the climb only takes one day (you typically begin your journey at midnight and reach the summit just before dawn). On this volcano, you can get very close to a recent volcanic eruption and witness its violent effects on the surrounding terrain— and you can even see the bubbling bottom of the caldera!

Many animals live in and around volcanoes, but nowhere is the wildlife more breathtaking than in the Serengeti. These famous grasslands, home to a range of animals from lions and zebras to hippopotamus and crocodiles, are adjacent to the Ngorongoro Conservation Area, making them only a short trip from any of the volcanoes you may choose to climb.

But the fauna are not the only spectacular feature in the Serengeti: Olduvai Gorge, in the eastern Serengeti Plains, is not only geologically amazing, but it is paleontologically significant as well. Olduvai, sometimes called the “Cradle of Mankind,” is a 48-kilometer-long gorge that was once a lake with thick layers of volcanic ash on its shores. About 500,000 years ago, seismic activity diverted a stream that began to cut through the layers of volcanic ash; the incision formed the gorge and revealed seven main ash layers, the oldest of which is 5.3 million years old.

The earliest artifacts of human ancestors at Olduvai are around two million years old, but fossil remains of early hominins have been dated to as old as 2.5 million years — and fossilized footprints from ancient hominins, dating back to 3.5 million years ago are on display at the nearby Olduvai Gorge Museum. Founded by archaeologist and anthropologist Mary Leakey, the museum contains many of the artifacts discovered in the region. There are also many wonderful plant fossils to be found at all stratigraphic levels. If you choose to visit the Olduvai Gorge and want to explore inside, guides are available to take visitors through it.

But the convergence of living fauna, human history and ancient geologic processes of Tanzania doesn’t stop there. The Mangapwani Coral Cavern on the island of Zanzibar is a karst cave, meaning that it formed when underground water dissolved surface limestone. The freshwater pool at the cave’s bottom was probably used as drinking water by Zanzibar’s early inhabitants. Vegetation grew over its main entrance, and the cave was forgotten until it was rediscovered as a source of freshwater for the household of a wealthy Arab landowner who sold slaves. After the slave trade was officially abolished in 1873, the Mangapwani caves were still used as a place to hide slaves before they were shipped abroad, an illicit trade that continued for many years after it was officially abolished. Despite the somewhat sinister purpose of the caves, its geology is truly amazing, making it worth a visit.

If fantastic and colorful corals are your taste, Zanzibar is still your ideal destination. The beautiful corals and diverse flora and fauna of Chumbe Island Coral Park have been preserved almost perfectly. At this amazing location, tourists can snorkel or scuba dive through the corals to experience the world of the shallow seas first hand. Out of the water, fossil corals line Chumbe beach, uniting the current and ancient ocean worlds. The various nature trails wind through the park and around intertidal pools in which fish breed and crustaceans and mollusks thrive. Chumbe Island Coral Park is a jewel of a pristine coral reef, and one that is readily accessible to tourists. Accommodation on Chumbe Island consists mostly of bungalows — some of which are even eco-friendly — for the perfect romantic (and green) honeymoon.

Tanzania is the perfect travel destination whether your interests lie in the splendor of the modern world or in the stunning remnants of a world long extinct. Few places so beautifully meld plants, animals and humans harmoniously with the planet on which they live.

Alexandra Ossola
Thursday, June 4, 2009 - 09:00

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