遥感教程第17部分答案¶
ANSWERS¶
` <>`__17-1: Using remote sensors: in chemistry, information on the composition of the atmosphere can be quantitatively assessed; in physics, the radiation laws discussed in the Introduction section can be tested; in botany, the distribution of major plant categories can be determined; and in geography, the precise outlines of coastlines and of river courses can be mapped. Many other answers are possible. **BACK**
` <>`__17-2: Look for the "Henry Mountains" in larger type, in the lower right corner. The Waterpocket Fold is to their left (labelled in small type). Much of what was shown in Section 2 of this fold is present in the sketch map. **BACK**
` <>`__17-3: Quite similar. Both tectonic regimes involve plate collisions. **BACK**
` <>`__17-4: The chief difference is the absence of well-defined ridges that rise above lower valleys, thus helping to outline the folding (the ridges in the Anti-Atlas and Pakistan scenes are hard, resistant sedimentary rocks that stand above the more easily eroded softer rocks in the valleys). In this Arabian Shield, most of the rocks have been metamorphosed into units that have much less variability in erosive resistance, so that ridges don't develop. There are some areas in which banding creates a crude allusion of ridges. But, overall, this scene is typical of the topographic expression of shield terranes. **BACK**
` <>`__17-5: The Pilbara block is much like a shield and, in fact, consists of typical shield crystalline rocks. The lower half of the image consists of sedimentary rocks (mainly) in structurally deformed basins; there are, however, few prominent ridge forms as are characteristic of fold belts. **BACK**
` <>`__17-6: The Mauna Loa (Hawaiian) structure is a basaltic shield volcano; it has numerous dark basalt flows extending down its sides. The Java volcanoes are andesitic in composition (higher silica; less iron) and lavas emanating from them are intermediate to light in color tone; these do not stand out visually in contrast and are hard to see at all in the Landsat image. **BACK**
` <>`__17-7: The word "dendritic" has a Greek root. It refers to a tree and its branches. Dendritic drainage has a master stream (the tree "trunk"), with tributaries (the branches) that themselves are fed by even smaller streams (the twigs on the branches). **BACK**
` <>`__17-8: The Ganges delta is huge, being almost two Landsat scenes wide. There have been many individual river distributaries (including from other rivers, such as the Hoogly River passing by Calcutta on the left of the image) that have built up the shore deposits over millions of years. The delta deposits have been dissected both currently and in the past by these distributaries (in the mangroves they are tidal estuaries) which have produced through back erosion the fingerlike peninsulas that extend to the coastline. In contrast, the Yukon delta has only a few distributaries that have yet to carve up the fanlike shape of the main delta. Neither delta is presently producing "birds-foot" extension deposits. **BACK**
` <>`__17-9: The fjord waterways are part of the famous inland passage through the Alaskan Panhandle and are frequented by many pleasure cruise ships (the "Alaskan Cruise" so commonly promoted in the Travel pages of newspapers and magazines) each late spring to fall. This brings tourism to the ports of call such as Juneau. **BACK**
` <>`__17-10: Over the short run, the islands are quite vulnerable to hurricanes and "Nor'easters". In addition to direct wind damage, maximized because so few trees are on the islands, the winds push the waves onto the islands, which are at most just a few tens of feet above sea level, and inundate beaches and homes built near them. Over the long haul, these islands may both be shifted by natural wave action and be gradually submerged if sea level continues to rise worldwide. **BACK**
` <>`__17-11: Caves. Most caves are made by dissolving limestone with water (usually slightly acid from CO2 within it). Sinkholes are formed at the surface in a similar manner (many sinkholes enlarge into caves below). This part of China also has numerous caves. **BACK**
` <>` _17-12：湖泊是充满水的洼地。在一个大致方向上，冰的前进或后退会导致冰川后退后，从延伸的洼地中挖出接受水的地方。在大尺度上，大湖是经典的例子，尽管它们并不一致。在冰川山脉中，冰川前的溪流都沿一个大致的方向从山顶流出。阿拉斯加的这些湖泊就是一个很好的例子：
` <>`__17-13: They will eventually fill up with more salts and most probably then with sediments that cover them. Lakes, in general, are transient geologically and disappear as they are filled and streams wander elsewhere to lower elevations, often forming lakes at their termini if the drainage is interior (i.e., doesn't reach an ocean). **BACK**
` <>` _17-14：是的，虽然这并不常见。如果是有植被的，覆盖物主要是草和专门的植物，也许是不需要富含粘土的土壤来生根和生长的小树。世界上大约90%的沙漠生物群落不以沙丘为主；事实上，适应低年降雨量的植物种类繁多，是大多数沙漠的特征。在美国，内布拉斯加州的沙山是由沙和粉土组成的沙丘的一部分（来源于风把冰川尘埃从沉积物吹到北方），形成于过去（不到10000年），该地区的气候更加干燥；现在，那里的半干旱条件用草培育部分覆盖物。这是一个沙丘的陆地卫星TM次新世，证实了草原的存在，主要在这些线性沙丘之间的低地或洼地（构成北美最大的沙丘场）中发育。
另一个沙丘支持植被的例子是在纳米比亚的卡拉哈里沙漠。这里的沙丘正在向北迁移，覆盖了自然植被和农场，随着更多的沙子继续移到图像顶部以外的草原上，一些生长仍然存在。
海洋海滩上的沙丘通常是由该生态系统特有的植被所稳定的。 **BACK**
` <>`__17-15: The glaciers themselves, when gone, would leave behind wide valleys whose cross-sectional profiles are U-shaped. The high mountains, from which the glaciers emanate, would be rugged, with steep angular slopes and thin ridges, having a topography much like the high Alps of Europe. **BACK**
` <>`__17-16: This is a thought exercise and requires no direct answer. **BACK**
` <>`__17-17: Again, a subjective action on your part. **BACK**
` <>`__17-18: There are many more ridges in the Elk terrane. These are closer spaced, hence the slopes are less wide (probably steeper) and the valley floors are narrow. **BACK**
` <>`__17-19: Clearly, the Elk terrane is higher than Sixes River. A large area of the Elk terrane is above 3000 ft whereas the Sixes River has only a moderate area as high as 2000-2500 ft. **BACK**
` <>`__17-20: Much of western Oregon is heavily forested and is a major source of timber. The squares are classic examples of the type of deforestation by clear-cutting that is carried out by the lumber industry. This is a significant part of the economy of this region. **BACK**
` <>`__17-21: It's subtle, but there appears to be a slighly closer spacing of ridges in the Yolla Bolly terrane compared with the Rogue Valley terrane. **BACK**
` <>`__17-22: Ridge density and ridge orientation, and to a lesser degree, hypsometric curves and maximum elevations. **BACK**
` <>`__17-23: The chief use of space imagery is that it provides a visual overview of differences in landforms/topography expression; it helps to pinpoint areas for quantitative analysis by conventional morphometric means. As stereo imagery becomes more common from spaceborne sensors, or elevation measurements are obtained by systems such as SRTM, the ability to make measurements now restricted to topographic maps will notably expand the use of images acquired from satellites or astronaut photography. **BACK**