Although less than 70 miles (110 km) from Boston and other large population centers, the trail is considered remarkably rural and scenic and includes many areas of unique ecologic, historic, and geologic interest.

Site specific activities enjoyed along the route include hunting, fishing, horseback riding, boating (on the Connecticut River), bouldering, rock climbing, and swimming.

[4][5][6] The southernmost 40 miles (64 km) of the M&M Trail traverse a northern section of the trap rock Metacomet Ridge which extends from Long Island Sound to the Massachusetts/ Vermont border.

[4] The trap rock ridges and talus slopes are also home to several unique microclimate ecosystems that support species of plants that are unusual or endangered in this part of New England, and are a seasonal migration path for raptors.

[7] Viewsheds from the ledges include agrarian land, suburbs, small towns, river corridors, the eastern Berkshires ridgeline, metropolitan Springfield, and the skyline of the University of Massachusetts Amherst.

[1] Where open to public access, the remaining 66 miles (106 km) of trail follows an elevated plateau of 400 million year old metamorphic rock punctuated by occasional monadnocks.

[8] The terrain is a rural and largely wooded, post-glacial landscape with sparse viewpoints, deep ravines, and a few bare mountain summits.

The trail follows the western edge of this plateau in a northerly direction, then jogs east along the Massachusetts/New Hampshire border before turning north again to reach Mount Monadnock.

The route was constructed utilizing newly blazed paths, abandoned farm roads, and existing hiking trails (many of them several hundred years old) where available.

Fires deliberately set in the early 19th century by nearby farmers concerned with wolves denning in blowdown snags resulted in the denudation of the mountain.

Since then, the summit has recovered to the degree that it appears natural and scenic, although it is still very barren and reminiscent of the alpine peaks of the White Mountains to the north.

Vegetation has begun to slowly reclaim some of the ledges and ravines, but the process of soil generation on windy slopes will likely take many hundreds of years.

[2] The geology and natural environment of the M&M trail can be divided into two distinct sections: the Metacomet Ridge of the Pioneer Valley and the upland plateau of central Massachusetts and southern New Hampshire.

Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance.

The basalt ridges are the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa.

Erosion occurring between the eruptions deposited deep layers of sediment between the lava flows, which eventually lithified into sedimentary rock.

The sedimentary rock of the Connecticut River Valley is also well known for its fossils, especially dinosaur tracks, which have been discovered in several locations near the ridges that the M&M Trail traverses.

Because the trap rock ridges generate such varied terrain, they are the home of several plant and animal species that are state-listed or globally rare.

[11][12] North of the Holyoke Range, the M&M Trail traverses an upland plateau composed of much older metamorphic rock, mostly schist, gneiss and quartzite.

The plateau, averaging 1,000 feet (300 m) above sea level, is geologically related to the higher White Mountains of New Hampshire, farther to the north.

[14] As the crow flies, the M&M Trail route is never more than a mile or two from a public road; however, cliffs and steep terrain on the Metacomet Ridge and on Mount Monadnock and other peaks make access much more difficult in some areas.

Trail descriptions are available from a number of commercial and non-commercial sources, and a complete guidebook with topographic maps is published by the Appalachian Mountain Club.

[1] Weather along the route is typical of Massachusetts and southern New Hampshire, with slightly warmer temperatures in the Connecticut River Valley versus the upland plateau to the east.

The Connecticut River is not fordable; the trail terminates where it meets it (one must walk or drive to the Northampton Route 9 bridge or arrange for boat passage to the opposite bank).

Poison ivy is native to the M&M Trail ecosystems, but it occurs with less frequency north of the Holyoke Range, and does not thrive on Mount Monadnock at all.

Except during the winter, trap rock ridges tend to be dry, leaving long stretches of trail with no dependable water source.

Many groups are invested in preserving the pathway and viewshed of the Metacomet-Monadnock Trail, including The Trustees of Reservations, Mount Grace Land Conservation Trust, Friends of the Mt.