A Tour of the World from Space - General Background- Remote Sensing Application - Completely Remote Sensing, GPS, and GPS Tutorial
A Tour of the World from Space - General Background

Enough of the heavy stuff for a while! Letís take a breather, have some fun, and just look at some stunning scenes that depict typical landscapes and urban centers of the world. This Section amounts to what can be called a "Travelogue", a pictorial journey across the world looking at places both well known and vistas that give a "flavor" to geographic regions as seen not only from the ground and the air, but now from orbital platforms in space.

The first part of this Section will concentrate on selected regions of the United States from the East to the West Coast. The second part consists of representative views of other countries of the World, organized and displayed by continents beginning with the rest of North America, Central America, South America, Europe, the Middle East and Africa, and Asia.

We will stress two major themes in each part: 1) the natural features of the regions we will visit; and 2) many of the principal and best known cities in various countries. The natural features are grouped into two broad categories, controlled by their underlying geology: 1) mountain belts and shields (igneous and metamorphic rocks; folded/faulted sedimentary rocks), and 2) largely horizontal sedimentary rocks (so-called platform [tectonically unactivated] setting). This map shows the global distribution of category 1 in color and 2 in white (blank).

Categories of geologically-controlled natural features.
As an example of some specifics associated with the first theme, we will show satellite imagery and ground photography of some of the highest mountain peaks worldwide:
Major mountains of the world.

This map includes many cities we will visit:

Cities of the world.

So, lets get started on the journey!

PART 1: ACROSS THE UNITED STATES

We set off by going on a simulated air vacation trip from one coast of North America to the other - going east to west, and pretend we can look out over large expanses of the ground, om effect from the Canadian border to the southernmost U.S. In so doing, we will gain a sense of the variety of landscapes that make this one of the most diverse and interesting continents on the globe. We will accomplish this journey by perusing various satellite scenes each typifying some specific region within the 48 conterminous states.

Many people, especially those who live near the East or West Coast of the United States, have flown on commercial aircraft across this country. Those who looked frequently out a window were certainly impressed by the ever-changing landscape. Each region has its own distinct character, expressed by combinations of topography, vegetative cover, and land use/cultural patterns. These characteristics are largely controlled by the underlying geology, climate, vegetative cover, population densities, and particular modes of infrastructure development for supporting human activities.

Some of you have been introduced to these ideas and relationships, if you have taken a course in Physical Geography. One element or theme in that course is the importance of physiography, a term which connotes "description of the landscape" at regional scales that describes the types and influence of landforms, soils, climate, vegetation, and hydrologic actions on the natural scenery. Each realm is a discrete physiographic province, which, once lived in, seems unique, so that we always sense a distinctiveness in the surroundings when visiting a particular province. We show a map of the physiographic provinces in the 48 United States below:


Physiographic Provinces of the United States.
From H.J. de Blij and Peter O. Muller, Physical Geography of the Global Environment, Figure 52-1, 1st Ed. © 1993. Reproduced by permission of John Wiley & Sons, Inc., New York.

This version of the Physiographic Provinces may prove simpler to remember the main subdivisions:

Another Physiographic Provinces map.

Five of the six mega-provinces in North America (excluding the Arctic Coastal Plains) extend into the U.S. Three national regions are subdivided by two or more provinces, as named. The Canadian Shield is part of the ancient craton or core of the continent and is marked by a dominance of Precambrian igneous and metamorphic rocks, which give rise to low hills and subdued mountain ranges. Being in the north, the colder, generally humid climate favors dense boreal forests with evergreen and birch trees. The dominant mega-province in eastern North America is the Appalachian Highlands, consisting of several provinces, which contain rocks ranging in age from about 570 to 245 million years (m.y.) They have been involved in several major episodes of mountain building, culminating in the Appalachian Revolution about 250 m.y. ago. The oldest rocks in the east, many of which are metamorphosed and invaded by igneous intrusions, comprise the Piedmont province, consisting of rolling hills and ridges. The structural bending of Paleozoic sedimentary rocks into folds often offset by faults produces a distinctive topography of dissected ridges that generally are now less than 1,220 m (4,000 ft) in elevation. This area encompasses the Newer Appalachians,, more commonly called the Valley and Ridge province. The surface has been worn down, after uplifts over the past 10 m.y, to form valleys with rolling terrain. To the west of the province is a broad area of uplifted but unfolded sedimentary rocks making up the Appalachian Plateau province. Over much of this province, erosion has carved out mountain-like terrain comparable in relief to the adjacent Valley and Ridge. Being in a humid, often warm climate the Appalachians are still heavily forested with deciduous trees except where cleared by humans for development.

The Interior Plains are underlain mostly by sedimentary rocks as old as 600 m.y. and young as 10-20 m.y. (in the western parts). These rocks are almost everywhere flat to subhorizontal, so that erosion has not carved out prominent mountain landscapes. The terrain is flattened further in the northern half by deposits from continental glaciers that covered the region during the last three million years. The Interior Lowlands seldom reach elevations above 460 m (1500 ft). They now support stretches of forests that remain after farmers cleared much of the land. These deciduous treescapes diminish to the west and south as grasslands take over. The Great Plains section consists of deposits of sediment brought eastward from the Rocky Mountains to the west. The deposits are piled up such that the elevations increase westward to 1525+ m (about 5,000 ft). Most of this land is either natural-grass rangeland used for grazing or farmland, with forests now being small and scattered.

In the southern U.S., but extending northward to New Jersey, is the Gulf-Atlantic Coastal Plain province, a flat lowlands of nearly horizontal rocks, laid down during the last 60 m.y. as marine waters repeatedly invaded the North American continent during variations in sea level. This region is predominantly farmland, although some parts are still forested.

The Western Mountains are composed of a number of diverse rock/structural units of differing ages and histories of orogeny (mountain-building). Although the rocks exposed can straddle a wide range of geologic periods, most of the events that produce the units took place in the last 70 million years. Because of differences in structural states, we conveniently break the eastern segment known as the Rocky Mountains, which can reach heights up to 4,420 m (14,500 ft), into three sections. The Colorado Plateau is an elevated (typically around 1,200 m [4,000 ft]) uplift of largely horizontal rocks, which have been cut into spectacular landscapes mostly covered with sparse desert vegetation. The Basin and Range province consists of rugged, often barren rock bodies uplifted along faults into elongated mountains separated by valleys with gentle sloping floors created by erosional fill from the higher ranges. Vegetation is mainly desert types that are subordinate in density of cover to the rocky soils that dominate the surface.

The Columbia Plateau is a region capped by volcanic flows (mostly basalts) extruded from fissures over the last 40 m.y. In places, the flat land is cut by deep canyons, but is also broken by older rocks sticking upward as pre-existing mountains that were not engulfed by the volcanic flows (which can be 1,200 m [4,000 ft] in thickness). The landscape in much of California and the western parts of Oregon and Washington is also mostly mountainous. The high Sierra Nevada is a great tilted fault block rising as high as 4,420 m (14,500 ft) and supporting fir and pine trees. It connects to the Cascades which are marked by numerous stratovolcanoes, more or less active in the last 20 m.y. Along the Pacific coastline are the Coast Ranges, still being actively warped by plate tectonic-driven compression. In California, between these mountain belts, is the Central Valley (subdivided into the Sacramento [north] and San Joaquin [south] valleys), a structural basin now receiving infill from the highlands. Its warm temperate climate allows extensive farming.

The Physiographic Provinces correlate well with the first-order (general) geology of the U.S. This is evident from the next map that includes not only the U.S. but Canada, Greenland, and the Caribbean. This map shows general structural units related to the provinces. (See also page 2-1b for related information). The term "craton" refers to the stable nucleus of ancient rocks that makes up most of the North American interior; platform denotes sedimentary rocks that cover the craton. Note that there are two main orogenic belts: the Appalachians on the east, with a present day passive tectonic margin, and the Rocky Mountains/Coast Ranges assemblage on the west, with an active margin (subduction; transform faulting).

Major geologic units (both structural and temporal connotations) of North America.

The map above alludes to something not yet stated. Geographers favor including all of Central America and the Caribbean as part of North America. This is justified by the fact that most of these areas are part of the N. American tectonic plate.

There is a general correspondence between physiographic expression as provinces and the general geology of each region. Here is a look at the U.S. Geological Survey geology map (emphasizes ages of the units) of North America:

Geologic map of North America.

As a generalization, red refers to exposed Precambrian rocks, purple to Lower Paleozoic, blue to Upper Paleozoic, greens to Mesozoic rocks, yellows to Cenozoic; and buffs to Pleistocene rocks.

Somewhat more detail is included in the U.S. Geological Survey map of the 48 contiguous United States:

The USGS map of the United States.

Working together, the U.S. Geological Survey (USGS) and the Environmental Protection Agency (EPA) used Landsat TM data to produce a general land cover map of the 48 contiguous states, published in 1992:

Land cover map of the U.S.
Legend for land cover map.

The Physiographic Provinces also correlate rather well with the different major classes of vegetation. Those in turn depend both on soils (which are dependent in various ways on the underlying geology) and climate (which also helps determine which soil types develop). Here is a general Vegetation Map of North America; the names in red are soil types (not treated here; surf the Internet under Soil Classification for further information):

Vegetation (and Soil Type) Map of North America.

Compare the major vegetation types on the map with this image of all of North and Central America, made from satellite inputs. You should be able to discern subtle to sharp difference in color tones - which correspond mainly to extent of vegetative cover - that match the map units fairly closely:

Near natural color image of North and Central America.

To provide you with a visual overview of the entire country, we display a mosaic of Nimbus Advanced Very-High Resolution Radiometer (AVHRR) false color images (see page 14-2 for a description of this sensor and its satellite platform).

False color Nimbus AVHHR mosaic image of the United States.

Alternatively, we could have reproduced one of several Landsat mosaics, such as the color versions produced by General Electric Corporation (for the National Geographic Society to celebrate the 1976 Bicentennial) or the first ever (in black and white) put together by the Soil Conservation Service (see page 7-3. Because resolution is not a critical factor at the small scales needed to portray the U.S. from coast to coast, we used the AVHRR mosaic.

Many people have some problems in locating specific cities or major localities, and good maps are not always available. We reproduce a U.S. geographic map here, and will do the same for Canada and Europe later in the Section.

Map of the U.S. showing major cities.

You may wish to get a better look at the space image appearance of your hometown or town where you now reside that affored by the U.S. mosaic. An AVHRR image and landform map of each state is accessible on a Web site produced by Applied Physics Laboratory of Johns Hopkins University in Maryland. To show you what to expect, here are the AVHRR and DEM topography (landforms; consult an Atlas to identify these) image you would get for the state of Wyoming.

AVHRR Color Composite of the state of Wyoming; vegetation in the mountains is purplish-blue and in the lower basins is mostly green.
Colorized Landforms Map of Wyoming made from DEM elevation data.

Although geography is the main theme of this Section, and this page, we will insert here a brief history lesson. We all know that Christopher Columbus is celebrated as the discover of the Americas (in fact, of course, the millions of native tribes people [some being the Indians of whom we are familiar] were here first [for at least 20000 and perhaps 40000+ years], and Norsemen probably visited Newfoundland around 1000 A.D.) In actuality he first landed in October, 1492 on an outermost Bahamas island (called Guanahani by its natives; renamed San Salvador by Columbus). Here are two views from space:

San Salvador from space; the island is 20 by 10 km in size.
Closer view of the south half  of San Salvador.

During his first journey, Columbus also observed the islands of Cuba and Hispaniola (today, Haiti and the Dominican Republic).

Columbus' first expedition.

By his fourth trip, he reached Venezuela and had landed in Mexico, Honduras, and Panama. But he never realized that he had discovered two huge new continents. To him these were islands in the New World which he ultimately did not believe were parts of India but perhaps were off its shores.

It remained for others to determine the vastness of the regions in the New World as it was first settled. Hernando Cortes invaded and conquered Mexico in 1519. Other Spanish explorers discovered Florida and started the first N. American settlement - today's St. Augustine - in 1565; Francisco Coronado and Hernando de Soto led expeditions into the interior (including the Mississippi River valley) of today's United States in the 16th Century. The Englishman John Cabot found the easternmost part of Canada (Nova Scotia) in 1497 - thus was the first to land on North America proper; Jacque Cartier (a Frenchman) sailed along the St. Lawrence River in 1535, thus establishing France's claim to Canada which remained French until the English victory at Quebec City in 1759 followed by the deeding of all of Canada to England in 1763.

The eastern U.S. was first occupied by Europeans with the failed English settlement in today's Virginia at Roanoke Island (1585) and the temporarily successful Jamestown in 1607 (the Virginia Colony thereafter grew fast in population). The English began to settle what they called New England during the early 17th Century (the Mayflower Pilgrims landed at Plymouth Rock in 1620). It is thus fitting to start our trip across the U.S. in Boston, Massachusetts.

Source: http://rst.gsfc.nasa.gov/