[8] Around 480 million years ago, geologic processes began that led to three distinct orogenic eras that created much of the surface structure seen in today's Appalachians.

[d] During this period, mountains once reached elevations similar to those of the Alps and the Rockies before natural erosion occurred over the last 240 million years leading to what is present today.

[9] The Appalachian Mountains are a barrier to east–west travel, as they form a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east–west.

This is a 2,175-mile (3,500 km) hiking trail that runs all the way from Mount Katahdin in Maine to Springer Mountain in Georgia, passing over or past a large part of the Appalachian range.

In north-central Alabama, Mount Cheaha rises prominently to 1,445 feet (440 m) over its surroundings, as part of the southernmost spur of the Blue Ridge Mountains.

The mountains formed during the Grenvillian era underwent erosion due to weathering, glaciation, and other natural processes, resulting in the leveling of the landscape.

The weathering of limestone, now exposed at the land surface, produces the lime-rich soils that are so prevalent in the fertile farmland of the Valley and Ridge province.

For instance, mafic rocks have been found along the Fries Fault in the central Blue Ridge area of Montgomery County, VA.[25] The Iapetus continued to expand and during that time bacteria, algae, and many species of invertebrates flourished in the oceans, but there were no plants or animals on land.

Then, during the middle Ordovician Period about 500 to 470 million years ago, the motion of the crustal plates changed, and the continents began to move back toward each other.

[28] The Acadian orogeny was caused by a series of collisions of pieces of crust from the Avalonia Terrane, sections broken off from continent of Gondwana, with the North American Plate.

The ocean continued to shrink until, about 270 million years ago, the continents that were ancestral to North America and Africa collided during the formation of the supercontinent Pangea.

[19] In the northern section the height of land lies on the inland side of the mountainous belt, and thus the main lines of drainage run from north to south, exemplified by the Hudson River.

[39] Eastern or Canada hemlock (Tsuga canadensis) is another important evergreen needle-leaf conifer that grows along the Appalachian chain from north to south but is confined to lower elevations than red spruce and the firs.

It generally occupies richer and less acidic soils than the spruce and firs and is characteristic of deep, shaded and moist mountain valleys and coves.

Other common trees are red maple (Acer rubrum), shagbark and bitternut hickories (Carya ovata and C. cordiformis) and black or sweet birch (Betula lenta ).

The foregoing trees, shrubs, and herbs are also more widely distributed in less rich mesic forests that generally occupy coves, stream valleys and flood plains throughout the southern and central Appalachians at low and intermediate elevations.

In the northern Appalachians and at higher elevations of the central and southern Appalachians these diverse mesic forests give way to less diverse northern hardwood forests with canopies dominated only by American beech, sugar maple, American basswood (Tilia americana) and yellow birch and with far fewer species of shrubs and herbs.

), black huckleberry (Gaylussacia baccata), a number of deciduous rhododendrons (azaleas), and smaller heaths such as teaberry (Gaultheria procumbens) and trailing arbutus (Epigaea repens ).

In contrast, the much rarer chinquapin oak (Quercus muehlenbergii) demands alkaline soils and generally grows where limestone rock is near the surface.

Among the most conspicuous is that of the introduced spongy moth (Lymantria dispar), which infests primarily oaks, causing severe defoliation and tree mortality.

But it also has the benefit of eliminating weak individuals, and thus improving the genetic stock, as well as creating rich habitat of a type through accumulation of dead wood.

the Adirondack Mountains, and Mount Katahdin have summits covered with true alpine tundra; these ecosystems are kept clear due to extremely harsh winter storms, and support a vegetation community more akin to that of the Arctic Circle.

Other common forest animals are the black bear (Ursus americanus), striped skunk (Mephitis mephitis), raccoon (Procyon lotor), opossum (Didelphis virginianus), woodchuck (Marmota monax), bobcat (Lynx rufus), gray fox (Urocyon cinereoargenteus), red fox (Vulpes vulpes) and in recent years, the coyote (Canis latrans), another species favored by the advent of Europeans and the extirpation of eastern and red wolves (Canis rufus).

Most frequently seen, however, is the eastern or red-spotted newt (Notophthalmus viridescens), whose terrestrial eft form is often encountered on the open, dry forest floor.

Salamanders and other amphibians contribute greatly to nutrient cycling through their consumption of small life forms on the forest floor and in aquatic habitats.

There are few lizards, but the broad-headed skink (Eumeces laticeps), at up to 13 in (33 cm) in length, and an excellent climber and swimmer, is one of the largest and most spectacular in appearance and action.

The French, British, and Spanish were among the major powers vying for dominance in the New World, and their interactions with indigenous communities and the Appalachian landscape shaped the course of history.

The French established settlements in the Great Lakes region and Canada, while the British colonies stretched along the eastern seaboard of what would become the United States.

In the United States, the proclamation aimed to curb westward expansion beyond the Appalachian Mountains to avoid conflicts with indigenous nations, leading to tensions between American colonists and the British Crown and contributing to the drive for independence.

In Canada, the proclamation provided a framework for governing newly acquired French territories, including Quebec, to ensure stability and control over the region.