Wanderlust World Wanderlust World The Appalachian Mountain system stretches over 1,500 miles from Alabama to Newfoundland. In the Mid-Atlantic, it broadens into a complex province of parallel ridges, deep valleys, and dissected plateaus. Both New York and Pennsylvania contain significant, geologically distinct sections.
Technically a dissected plateau, not a folded mountain range. Formed from Devonian-age river delta sediments (Catskill Delta) uplifted and deeply incised by streams. Characterized by steep, clove-shaped valleys (cloves), sheer escarpments (the "Catskill Front"), and flat-topped summits (e.g., Slide Mountain, 4,180 ft - highest in Catskills). Part of the Appalachian *Plateau* province. Famous for forests, waterfalls, fly fishing, and the "Catskill Park" Forest Preserve.
Extends from the Catskills west/southwest along the Southern Tier (Chautauqua, Cattaraugus, Allegany counties). A deeply dissected, rugged plateau of horizontal sedimentary rocks. High, broad hills (2,000–2,500 ft), narrow valleys. Includes Allegany State Park. The plateau continues south into Pennsylvania.
Geologically separate (Grenville Province, ancient metamorphic core, related to Canadian Shield). Not part of the Appalachian orogeny. Often grouped geographically but distinct structurally.
Pennsylvania showcases the quintessential Appalachian structure: long, parallel, NE-SW trending ridges and valleys.
Formed by intense folding and faulting of Paleozoic sedimentary rocks during the Alleghenian orogeny. Resistant sandstone/quartzite forms long, even-crested ridges (Tuscarora, Jacks, Bald Eagle, Blue, Kittatinny/Blue Mountain). Softer limestone/shale erodes into broad, fertile valleys (Cumberland, Lebanon, Lehigh, Wyoming Valleys). The Great Appalachian Valley (Cumberland/Lebanon Valley) is a major north-south corridor (I-81).
Northwest of the Ridge-and-Valley, the rocks are flat-lying but deeply dissected by the Allegheny, Susquehanna, and Ohio River systems. Rugged, high-relief topography (not flat plateau). "Pennsylvania Grand Canyon" (Pine Creek Gorge). Highest point: Mount Davis (3,213 ft) on Negro Mountain (actually in the Appalachian Plateaus province, near Maryland border).
Part of the Allegheny Plateau but higher, more rugged. Includes Laurel Ridge, Chestnut Ridge. Ohiopyle State Park (Youghiogheny River gorge), Fallingwater. Transition to the Appalachian Plateau of WV/OH.
Part of the Appalachian Plateau (Glaciated Plateau section). Broad, flat-topped mountains (2,000–2,200 ft), numerous glacial lakes, wetlands, thick forests. Distinct from the sharp ridges to the south. Popular recreation area.
The Appalachian structural grain (NE-SW) is continuous. The Ridge-and-Valley of PA connects to the Hudson Valley/Highlands of NY. The Allegheny Plateau is a continuous physiographic province across the border. The only major break is the Hudson River Valley, a lowland corridor separating the New England uplands from the main Appalachian chain.