The Nordicversion of Old Faithful is Strokkur, in Iceland Figure 3.. Geysers have individual schedules: a geyser at the south end of Lake Bogoria formerly Hannington, Kenya, erupts about
Trang 1announcing the schedule of eruption The Nordic
version of Old Faithful is Strokkur, in Iceland
(Figure 3) Geysers have individual schedules: a
geyser at the south end of Lake Bogoria (formerly
Hannington), Kenya, erupts about every 10 minutes, whereas Beehive geyser, in Yellowstone, erupts only once a year, and a geyser at Rotorua, New Zealand, erupts four times a week Changes in rainfall patterns can affect geysers; the Lake Bogoria geyser can tem-porally cease activity if the lake level gets too high, and the Great Geyser in Iceland, though active for
8000 years, now has to be stimulated by an injection
of soap powder
Sinter and Travertine Terraces
Hot waters dissolve various chemicals as they traverse underground rock channels When hot waters exit at surface openings, the dissolved chem-icals are precipitated and form cowls or cones around the exit fissure or aperture If the waters stream downslope, they may form spectacular ter-races The pink terraces at Rotorua, New Zealand, were long famous but were destroyed by earth-quake action, and the best example now extant is the magnificent organ-pipe terraces at Mammoth Springs, Yellowstone, Wyoming (Figure 4) Such terraces are commonly composed of calcium car-bonate and are referred to as tufa, where they are carious, or as travertine, where they occur in massive layers Where such deposits are siliceous, they are sometimes referred to incorrectly by these terms, and are best referred to as ‘siliceous sinter’ (calcar-eous deposits are also sometimes referred to as
‘calcareous sinter’)
Figure 4 Mammoth Hot Springs terraces, Yellowstone National Park, Wyoming, USA Reproduced from Science Photo Library.
Figure 3 Strokkur geyser, Iceland Reproduced with permis
sion from Green J and Short NM (1971) Volcanic Landforms and
Surface Features: A Photographic Atlas and Glossary New York, Hei
delberg, Berlin: Springer Verlag.
108 GEYSERS AND HOT SPRINGS