With the overview established on the first page for describing and interpreting the various landscapes that make the U.S. so picturesque, we now embark on a simulated flight over the continent, using mainly Landsat images to portray typical surfaces in many of the provinces discussed above. We start on the East Coast in Massachusetts (most of which is also in a lithologically distinct part of the Appalachians) and will proceed westward along a meandering line that brings us into northern California. But note: On this first page we will roam up and down the East Coast, geologically showing regions consisting of young Cenozoic rockss but also areas underlain by ancient Paleozoic rocks that relate to the Appalachians (treated more specifically on the next page).
We will start our transcontinental flight from Logan International Airport in Boston. We see it first as a Digital Globe/Google image and then as an aerial view that might be what an airlines pilot notes on approach:
Let us present a framework for the journey's beginning by looking at this large scene from space, which is a MODIS wintertime image that extends across the New England Maritime physiographic province. The New England states of New Hampshire, Massachusetts and Connecticut were part of the original 13 colonies at the time of the American Revolution. Vermont split from New Hampshire in 1777. Maine was an exclave of Massachusetts until 1820, when as a result of the growing population, it became the 23rd state on March 15 under the Missouri Compromise. This state is almost as large as the 4 original states.
Lets zero in on the starting point of our trans-continental air flight. The summertime Landsat image below covers metropolitan Boston, eastern Massachusetts, Cape Cod, and Providence in Rhode Island. The geology of this region is governed by ancient crystalline rocks that form the lower units in the now much-eroded eastern Appalachian mountain system. The entire region has been glaciated.
Geologically, this region is part of the Appalachian Mountain Belt that passes northward through Nova Scotia and Newfoundland. Most of the rocks underlying the province are igneous and metamorphic. We usually associate these rock types with the deeper parts of an orogenic belt, where temperatures and pressures were higher during their formation (this belt is within the Appalachians; see next page). Their presence at the surface today implies extensive erosion that stripped away the overlying sedimentary rock units after the main episode(s) of mountain-building and uplift. The landscapes typical of New England resemble parts of the Canadian Shield. Flatter areas are interspersed with low mountains, although peaks, such as Mt. Washington in New Hampshire and Mt. Katahdin in Maine, reach elevations exceeding 1,890 m (6,200 ft) and 1,590 m (5,200 ft), respectively. The rocky soils in the region do not favor farming, so that much of the land remains in forests. The predominance of deciduous trees accounts for the widespread reds in this false color composite (above). Most of New England experienced one or more advances of the Pleistocene continental glaciers that removed soils, laid down deposits, and carved out lakes.
The bluish area along the Massachusetts coast is the central part of greater Boston whose harbor lies within Boston Bay. As seen by the Landsat-4 TM, that area looks like this:
This map of Greater Boston should help you to get your bearings. Fit the scene above and the scene below in it.
An astronaut photo taken from the International Space Station shows part of inner Boston and sections to its north in some detail. The center of the city is the Boston Common; the large Logan Airport makes this a frequent destination for travelers, including those going to Europe.
Now for a history lesson. Look at this map of Boston in 1775. Compare that with the map above and the ISS image. Before reading on, try to single out the main differences:
There appear to be many changes since the Revolutionary War. At that time, Boston itself was almost an island, with only a narrow stretch of land - the Boston Neck - connecting it to the mainland. Both the Boston Harbor and the Back Bay (Charles River) were much more extensive then. What has happened should be obvious (certainly not sealevel fall, exposing land, since modern sealevel is rising slowly): huge amount of dirt fill have been dumped into the harbors, creating new land and expanding the Neck to its present width. The Charles River has been narrowed (but still wide enough upstream for sailboating). Noodle Island has been added to, enough to allow construction of today's Logan International Airport.
The Revolutionary War began on April 19, 1775 at Lexington and Concord, suburb towns about 35 km west. The first important battle took place on June 17, 1775 at Breeds Hill/Bunker Hill just north of Boston proper (then, a town of about 16000 people). Bunker Hill rose 110 ft from the river. This fight, commanded by British Gen. Wm. Howe, involved several charges by the "Redcoats" under General Thomas Gage that finally drove off the Colonial Minutemen and other militia under General Israel Putnam (although Col. Wm. Prescott was the actual field commander; many historians credit Putnam with the immortal command "Don't fire until you see the whites of their eyes."). Although technically this was an English victory, their heavy losses - 226 dead (Americans 140 killed) and 828 wounded - shook their confidence in an easy quelling of the Rebellion
Gen. Howe thereafter holed up in Boston, surrounded by Americans to the north and west. His failure to capture the Dorchester Heights proved fatal. In the dead of winter, the Americans led by Henry Knox hauled captured cannon from Fort Ticonderoga in New York (which had been stormed earlier by Ethan Allen and Benedict Arnold) through snowstorms back to Boston - a feat requiring two months. General George Washington, the newly appointed Commander-in-Chief, set the cannon up on Dorchester Heights. The fear of uncontested bombardment eventually forced the British to evacuate Boston (by sea, going first to Nova Scotia, until attacking Long Island and then New York in August) on March 17, 1776 ("Patriots Day"), leaving New England untouched for the rest of the war.
This GoogleEarth image portrays most of present day downtown Boston (area at word "highway.." in the ISS image). Note how some streets curve. One can actually start down a street going west and while staying on this street end up at Boston Harbor on the east. .
An aerial oblique photo shows this downtown area, the Boston Commons, Back Bay, and the John Hancock building (foreground).
Here are an aerial view showing the campus of the Massachusetts Institute of Technology (MIT) on the Cambridge side of the Charles River and again in a 2 meter color space image made by the Quickbird satellite.
In recent years to offset the traffic snarls and confusion, tunnels under the Bay and broad limited access highways right through town have improved the traffic flow. This Quickbird image shows a part of this transit system, along with striking new modern tall rises:
A conspicuous feature in the Landsat scene is Cape Cod, an east-west landmass built from extensive end morainal deposits that mark the southern boundaries showing how far glacial ice sheets advanced. A closer look by radar shows the many small lakes in the Cape (note the canal shortcut):
The sharp bend that ends at Sandy Hook represents, in part, modifications brought on by ocean-wave action. South of the Cape are the islands of Nantucket and Martha's Vineyard, also originating from fluvioglacial action. All three are noted vacation spots. Lowlands associated with drowned rivers make up Buzzards Bay off the west end of the Cape and Narragansett Bay below Providence, Rhode Island.
North and east of Boston is the home of the "Down Unders" - the citizens of Maine. Here is coastal and inland Maine in summer and again in winter:
The igneous-metamorphic rocks underlying much of Maine were extensively glaciated in the Pleistocene. Brown areas in the winter scene - set off by snow - are low hills which are covered by fir trees and some birch and maple trees. Lewiston, Brunswick, Augusta, Waterford, and Bangor are in this scene (since your atlas should be open, find them). The indentations caused by the glaciation are partly responsible for the rugged irregular coastline that is being inundated by post-glacial sealevel rise. The last landmass on the right of the winter image that projects into the sea is Mount Desert, on which Bar Harbor is situated.
Mount Desert is the most popular tourist destination in Maine. Here is a space image of the island and a ground scene showing its rugged Cadillac Mountains:
New England is a favorite destination for tourists in part because it has so many lovely, quaint small towns. These abound in Vermont and New Hampshire. All of the latter state and part of Vermont are shown below (note that both states are mainly low mountains and many lakes; the cold winters are ideal for skiers). Beneath it is the town of Portsmouth, NH, near the coast and a splendid place to sample the New England flavor.
Near the bottom left of the first Landsat scene above is another large blue area - the characteristic signature of a metropolitan region. Its location on Naragansett Bay gives its identity away - it is Providence, capital of Rhode Island, the U.S.'s smallest state. Here is a picture of its downtown buildings:
This is Providence, as seen from space (much of the green is suburban, with a moderately high density of homes):
Southern New England is also made up of crystalline rocks that are an extension of the Piedmont to the southwest. The Landsat scene below shows early leafing of trees in Connecticut. The Hudson River is on the west; the smaller Connecticut River to the east. New Haven (home of Yale University) is the blue patch along the upper reach of this latter river. The terrain in Connecticut is mostly low rolling hills, cut into crystalline bedrock (its fracturing is faintly evident).
The capital and largest city in Connecticut is Hartford, on the Connecticut River. This is often cited as the Insurance Capital of the U.S.:
On page 4-3, we commented on the concentration of population in the so-called East Coast Metropolitan Corridor that extends from Boston through New York City, then Philadelphia and Baltimore-Washington to Richmond. Much of that corridor is dramatically highlighted in this nighttime scene from space, because of the bright lights of the cities and their suburbs:
At this early stage in our trip, we will set a precedent that will recur on most of the other pages covering the areas visited in the cross-country journey above the U.S. We will depart significantly from the main geographic region featured on each page to look at other regions often considerable distances away. Let us start with a look with the state of New York, shown here as a mosaic using Landsat and other satellite data. We will look at 4 principal features: 1) New York and Long Island; 2) the Adirondacks; 3) the Finger Lakes; and 4) Buffalo and Niagara Falls.
This is a general physical features map of New York state:
We start first with the greater New York City metropolitan area, which you earlier saw imagery from on page page 4-2. (Check the map on that page for locations of the 5 New York City boroughs.) This next image includes western Long Island, the 5 boroughs of New York city, and many northern New Jersey towns, has a population of more than 21 million. Across from New York City itself are several New Jersey cities with high population densities. This photo, taken from the International Space Station, shows Manhattan, Jersey City, Hoboken, North Bergen, Kearney, and a bit of Newark:
Manhattan, of course, is one of the great cities of the world - the heartstone of cosmopolitan living. This ground photo shows the Empire State Building in midtown and Lower Manhattan in the background.
Many who work in New York City live on Long Island to the east. Long Island, like Cape Cod, owes its origin to Pleistocene glaciation. A series of moraines make up the land mass that lies between Long Island Sound and the Atlantic Ocean. Here it is from space:
The image below is almost an oddity. It is a radar view that shows most of New York City and the western part of Long Island. What was intriguing is the "apparent" jagged coastline of Long Island Sound, and to a lesser extent the Atlantic coast beaches; this is somewhat illusory as an artifact of the radar imagery.
The Adirondacks and the Catskills are the two principal mountain groups in New York State. They are both displayed in this perspective image which was made from Landsat and SRTM data combined:
The Catskills (right side of the above image) are dissected Paleozoic sedimentary rocks. You saw a Landsat mosaic of the Adirondacks (left side of image) near the bottom of page 2-8.. The Adirondacks are an extension of the Canadian Shield and consist of Proterozoic (Precambrian) metamorphic rocks and some igneous rocks. They are distinctly mountaineous (their highest peak is Mt. Marcy at 1030 m [5345 ft].
While we are on the subject of mountains in the Northeast, most of the principal groups given specific names are shown in this map:
West of these mountains are the Finger Lakes, another popular recreational area. The lakes were scoured out by continental glaciation and then filled by drainage waters after the ice disappeared. We see them in this astronaut photo and identify them from the map below it (note where Syracuse and Rochester are):
At the west end of New York State, between Lakes Erie and Ontario, lies Buffalo and to its north Niagara Falls. We see these first in a Landsat subscene, then the Falls from SPOT and in an IKONOS image:
Here is a panoramic view looking south at the American Falls (left) and Canadian Falls (right). The Niagara River (less than 12000 years old) flows from Lake Erie to Lake Ontario (north) and passes over the Niagara Escarpment (Silurian) which is the reason for the Falls (which are slowly receding southward by undercutting erosion):
In the remainder of this page we will examine two segments of the very extensive Atlantic-Gulf Coastal Plains and Piedmont Provinces that begins in New Jersey (to its north, this unit is now almost entirely under the sea as part of the Atlantic Shelf) and continues along the Atlantic Seaboard (Florida is usually considered a special landmass included in Coastal Plains but with a different geological history) and then wraps around the coastline of the Gulf of Mexico, with the Coastal Plains continuing south to the Tex-Mex border (and beyond). The map below shows the Piedmont of the U.S.; every area to its east and south is the Coastal Plains:
Much of New Jersey is rural and supports farming in the Coastal Plains which make up its southern 2/3rds (Piedmont and a little Valley and Ridge in the northern segments). Its coastal region is popular as a seashore vacation spot. Much of its coastline consists of barrier islands; inland are woods still not cleared (the Pine Barrens):
Barrier islands are elongate, wide mounds of sand built up when these particles are carried by waves that strike the coastline, loose their velocity (carrying power), and deposit the load along the shore. Barrier islands occur along much of the Atlantic coast from New Jersey south to southern Florida.
We look next at the largest city in Delaware ("The First State"), Wilmington. The Christina River flows into the Delaware River (off the image to the right). Parts of the town lie on the Piedmont; other parts to the south are on the Coastal Plain:
As seen from the I-95 Interstate by-pass, this is Wilmington's skyline:
Going southward on the Piedmont, we next note the present day capital of Virginia, and onetime capital of the Confederacy, Richmond, on the James River:
We travel next to the coastal cities in southeastern Virginia. It may surprise one to see how extensively built up the region is. Look first at the map (Norfolk is not named but is at the Interstate 64 and 564 signs; News is part of Newport News) and then the Landsat image:
The northern edge of the Great Dismal Swamp is in the SW corner of the image. The region contains the home base for the U.S. Navy's Atlantic Fleet (including aircraft carriers). NASA's Langley Research Center (mostly aeronautics) is located in Hampton:
While still in the Coastal Plains, let's look at a popular vacation spot in the East: the Outer Banks of North Carolina. The Banks are a series of barrier islands built up over many millenia by waves carrying sand ashore as deposits that remain stable except during nor'easters (a fierce storm) and hurricanes that erode the beaches.
Then we will move into interior North Carolina, in the Piedmont just west of the Coastal Plains. We will look at three well known cities - Raleigh (home of North Carolina State University), Durham (Duke University), and Chapel Hill (University of North Carolina). In between them is the famed Research Triangle, the largest of its kind in the U.S. First locate them in this Landsat image (use the water reservoirs as a guide), aided by the map:
The largest of the three cities is Raleigh (about 350,000):
This late Fall image taken by Landsat covers the Atlantic Coastal Plain of part of South Carolina, much of which is now farmlands. Coastal pines dominate the dark areas near the coast. The Santee River has been dammed at Lake Marion, which drains into Lake Moultrie.
At the end of the drowned river valley coming off Lake Moultrie is the famed city of Charleston, rich in ante-bellum homes. This city, along with Savannah, GA and New Orleans, LA have well-preserved sections that are a hallmark of the Deep South. Charleston was much involved in both the Revolutionary and Civil Wars. The main city is a "Peninsula" formed at the confluence of the Ashley and Cooper Rivers. Here is a close-up made from Landsat-7 imagery.
A general aerial view of Charleston appears next. Along the eastern waterfront are some of the old homes of Charleston. These homes postdate those burned in the Revolutionary War, when Sir Henry Clinton captured the city at the start of the final (southern) phase of battle that ended with Yankee victory at Yorktown.
But Charleston is even better known as the town in which the Civil War began. The first shots were a cannonade of artillery fired across the harbor into the Union's Fort Sumper which was on an island loosely attached to the coastal wetlands. The fort was forced to surrender.
Another city of Civil War fame is Savannah, GA, less than 100 miles to the south.
Savannah was the destination of Union General Wm. Tecumseh Sherman at the end of his (in)famous march through Georgia after the fall of Atlanta. The city still has many antebellum homes (he declined to destroy them, unlike his actions at Atlanta), which occupy the conspicuous city blocks that are true "squares".
We will see several other space images of the Coastal Plains (for example, New Orleans, LA) elsewhere in the Tutorial.
South of Georgia is, of course, Florida. Most of that state does not fit the classic Coastal Plains category. Florida, geologically, is an arch added to the North American continent relatively recently. Most of its bedrock is limestone. Here is an unusual false color image of the entire state:
We saw Miami and Orlando in Section 4. Here we elect to represent Florida by its two big Gulf of Mexico cities - Tampa and St. Petersburg: