Arusha National Park (Mount Meru)

Abstract

The Arusha National Park, northern Tanzania is dominated by Mount Meru, which at 4,565 m is Africa’s fourth highest summit. Meru is a giant stratovolcano, part of the Younger Volcanism located on older, faulted volcanic terranes in the northern Tanzania divergence. The main cone has a diameter of 25 km. It was built up from numerous, explosive, Plinian-style eruptions that occurred between 0.20 Ma and 80,000 BP. The most spectacular feature of the volcano is a horseshoe-shaped caldera with an estimated age of 7,800–7,000 BP. The western side of the caldera reveals sheer inner walls and is capped by a rocky summit ridge. The caldera contains the 1,067-m-high Ash Cone, an unconsolidated pyramid of ash and cinders, which is one of the youngest volcanic features of Meru. The collapse of the eastern sector of the cone produced a large debris avalanche deposit (DAD), the Momella event, which extends over 35 km onto the lower slopes of Kilimanjaro. The caldera collapse and Momella event can be compared with the catastrophic eruption of Mount St. Helens in 1980. The avalanche at Meru was far larger and carved out a distinctive undulating terrane that contains the Momella Lakes, important habitats for migrating birds. The montane forests that girdle the lower and central slopes of the mountain are particularly extensive and are refuges for large mammals and numerous species of birds. The slightly older Ngurdoto Volcano, which is situated in the southeastern arm of the park, includes a well-preserved summit crater protected from visitors. Meru is gazetted as an active volcano (the last activity was in 1910) and should be monitored as potentially hazardous, particularly in light of the explosive style of volcanism and proximity to the regional town of Arusha.