China
Africa
Explore chapters and articles related to this topic
Sediments and Sedimentary Rocks
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Alpine glaciers, sometimes called valley glaciers, are much smaller than continental ice sheets. There are many alpine glaciers around the world, but counting is problematic because many are disappearing and others are very small. They are found in most major mountain ranges worldwide. Alpine glaciers flow down mountain valleys, beginning at high elevations in bowl-shaped valleys called cirques. Some alpine glaciers exist only in a small cirque in upland areas, but many glaciers flow long distances downhill. The lengthiest glaciers in the world, such as the Fedchenko Glacier, Tajikistan, are up to 100 kilometers (60 miles) long. The longest glacier in North America, the Nabesna Glacier in the Wrangell Mountains, Alaska, is more than 80 kilometers (40 miles) long. The glacier shown on the right in Figure 8.29 (Switzerland’s Aletsch Glacier) is the largest glacier in Europe’s Alps. It is shrinking today but had a length of about 23 kilometers (14 miles) in 2014.
Glaciers and glaciation of North Island, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2021
Shaun R. Eaves, Martin S. Brook
This southward-draining cirque glacier is situated below the summit peak Tahurangi, and between Skyline Ridge to the west, and Girdlestone Peak to the east (Figures 2 and 8A). Heine (1963) reported the glacier terminus at 6800 ft (c. 2050 m asl). Keys (1988) recorded c. 250 m terminus retreat, and c. 30 m surface lowering in the intervening period, with the glacier now terminating immediately above a steep rock cliff. Brook, Dean, et al. (2011) analysed interannual changes in the surface area of Mangaehuehu Glacier between 1988 and 2007 using oblique aerial photographs. Correlation analysis between the observed glacier area changes and a series of meteorological data and climatic indices found that ablation season temperature is a key control on the interannual fluctuations of glacier size. Observations of this glacier over several summers (2011–present) indicate winter snow preferentially persists on the western side of this glacier, in the lee of Skyline Ridge. This is illustrated by the convex glacier surface in the lee of this ridge (Figure 8A). This suggests southeastward wind transport of snow from the planar slopes to the west may be an important source of accumulation for this glacier.
Lithostratigraphy of Paleozoic metasediments in southern Fiordland, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2023
Richard Jongens, Ian M. Turnbull, Andrew H. Allibone
A highly variable succession of biotite, calcic and quartzose psammite, pelitic schist, marble, and quartzite in the Dark Cloud Range (Figure 4E), conformably overlying Long Sound Calc-silicate (Powell 2006), is here named the Prong Lake Formation. This is the structurally uppermost Cameron Group unit preserved. The name Prong Lake Formation replaces the informal Chankly Bore Formation used by Powell (2001, 2006), derived from an informal name for hills west of the lower Long Burn. The type section suggested by Powell (2006) begins near the contact with Long Sound Calc-silicate at the outlet of a tarn at 1128880E 4904120N, and follows a cirque headwall anticlockwise to spot height 1246, southeast of Prong Lake at 1127850E 4904730N (structural top).
Geology of New Zealand’s Sub-Antarctic Islands
Published in New Zealand Journal of Geology and Geophysics, 2019
James M. Scott, Ian M. Turnbull
The larger major valleys on Campbell Island/Motu Ihupuku have shallow U-shaped profiles, often truncated at their heads or down-valley ends by marine erosion. The main harbours are also of glacial (fjord) origin (Fraser 2009) with a moraine deposit forming the infamous Terror Shoal off Shoal Point and another forming a moraine off Boyack Point (Rainsley et al. 2018). The shallow barrier at the mouth of Perseverance Harbour is volcanic in origin, not glacial (Fraser 2009) or a long-shore drift deposit (cf. Quilty 2007). Glacial cirque topography is well developed about many of the higher peaks, particularly Mt Honey, with over-steepened headwalls, large erratic boulders and conspicuous and often semicircular lateral-terminal moraine loops (Figure 8A, 8B). A cirque with a semicircle of lateral and terminal moraine lies on the north side of Mt Dumas; the till is massive, poorly sorted muddy pebbly to cobbly gravel (Turnbull et al. 2004) (Figure 8C, 8D). On the northeast and south faces of Mt Azimuth, tiny subdued terminal moraine barriers lie well up-slope of the lower U-shaped valleys. Glacial deposits perhaps older than the cirque moraines occur in Hooker Valley (McGlone et al. 1997) and a larger lateral-terminal moraine sequence is especially prominent in the valley of Northeast Stream and in Northeast Harbour (Marshall and Browne 1909; Oliver et al. 1950). The flat spurs south of Beeman Hill and between Tucker and Camp coves are underlain by poorly exposed fluvioglacial deposits (Oliver et al. 1950). Small patches a few metres across of indurated pebbly to bouldery till, very similar to that on Mt Dumas, occur along most coastal outcrops. Flow-line modelling suggests that the moraines within the larger valleys may date from around 62–72 ka (Rainsley et al. 2018).