Page 69 - Volcano and Geothermal Tourism

46 Africa

Red Sea and the Gulf of Aden Rifts. The northern than 600m from a part of the barren Danakil
part of the Afar Triangle is a topographically well depression which is below sea level. Erta Ale
defined depression, sharply limited on both sides contains a 0.7 × 1.6km eliptical summit crater
by steep scarps of Paleozoic and Mesozoic origin: housing two steep-sided pit craters. Fresh-looking
the Ethiopian escarpment to the west and the basaltic lava flows, coming from eruption fissures,
Danakil horst to the east, which runs parallel to the have poured into the caldera and locally overflowed
Red Sea coast of southern Eritrea. The Ethiopian its rim (LeGuern et al, 1979; Acocella, 2006).
rift floor rises to a height of over 1800m at the During 1967–73 LeGuern et al (1979) documented
watershed north of Lake Ziwai and then descends overflows from the lava lake (70–200m across) that
northwards while spreading into a wide plain, areas filled the north part of the 700 × 1600m summit-
of which in the Danakil Depression are below sea crater complex to a depth of 100m by January
level (Mohr, 1960). 1973. Continuous overflows from the southern
Due to the ongoing divergence of the African lava lake (100m across) beginning in 1971 had
and Arabian Plates, Saudi Arabia has drifted away covered the entire crater floor, and lava flowed
from the rest of the African continent, forming the down the south flank by late 1973.
Red Sea. Where the Red Sea meets the Gulf of One of the authors (Edelman) visited Erta Ale
Aden a spreading centre has been developing volcano in November 2002; between 1998 and
under Africa along the East African Rift Zone. 2001 this had been impossible due to the fact that
Geologists believe that if spreading continues the the Danakil Desert was off-limits for tourists and
three plates that meet at the edge of the present- foreign researchers because of hostilities between
day African continent will separate completely, Ethiopia and Eritrea. During a six day stay on Erta
allowing the Indian Ocean to flood the area and Ale, members of the expedition descended onto
making the easternmost corner of Africa (the the terrace adjoining the lava lake in the active
Horn of Africa) a large island. southern pit crater in an attempt to obtain fresh
Thus the Afar Region (or Danakil) depression lava samples and temperature data. Since the level
is one of the key regions for the geology of East of the lake was very low at this time the recovery
Africa, located as it is, at the intersection of three of samples turned out to be difficult and finally
of the main structural units affecting the Earth had to be abandoned due to the dangerous
crust in that zone – the Red Sea, the Gulf of Aden instability of the crater walls. Several collapse
3
and the East African Rift. In spite of its geological events involving an estimated volume of 20,000m
importance, Afar has been neglected for a long were observed (Figure 3.1).
time by geologists in favour of more hospitable
regions of the rift zone, mainly because of The lava lakes of Erta Ale
difficulties with access and security. The first Just a handful of volcanoes in the world house
systematic field mapping and sample collecting active lava lakes. The most prominent example is
were undertaken by a French-Italian geological Kilauea on the Big Island, Hawai‘i which has
team in the winter of 1967–68 (Barberi and Varet, frequently housed small lava lakes in recent years
1970). Even until the 1980s the local Afars were and indeed had the first touristically exploited lava
considered to be hostile towards foreigners. Setting lake, which was active in the huge Halema’uma’u
foot on their land without permission could even crater until the powerful 1924 eruption. All other
be fatal, since the Afar tribes were known as trophy lava lakes are situated in poorly developed and/or
hunters, mainly focusing on the male genitals. very remote areas, such as those at Erta Ale and
Nyiragongo (DRC), or at Mt Erebus in the
Erta Ale: ‘The glowing eye of the Antarctic. The summit caldera of Erta Ale is
Danakil Desert’ renowned for two long-lived lava lakes (Figure
Erta Ale is the most consistantly active volcano in 3.2) – a larger, currently inactive northern lava lake
Ethiopia and the namesake and most prominent and a smaller, southern lava lake – located in two
feature of the Erta Ale range. It is a huge basaltic separate pit craters that have shown activity since
shield volcano which rises to a height of more at least 1967, or possibly since 1906 as reported by

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