This area, the Yukon Flats, is bounded by both the Yukon and Porcupine Rivers and is centered around the Fort Yukon area. The rest of Alaska, including the highly deformed Brooks Ranges, has moved to some extent, although the amount, nature, and timing of movement is poorly understood and highly controversial. Several are visible in the Landsat mosaic. After earlier orogenic events in the Jurassic, climax deformation of the Brooks Range occurred in the Cretaceous, with strong northward thrusting of thin-skinned tectonic displacements. More orogenic activity took place in the Late Tertiary and Quaternary, further distorting the range to its present concave northward bend.
Dissected plateaus are present.
T-10.4 Most of southern Alaska is characterized by narrow arcuate zones of strongly folded and faulted metamorphic and intrusive rocks and zones of compressed strata, much of whose structure is mainly the result of subduction. The Alaska Range is a large synclinorium of uplifted rocks cut by numerous faults, accentuated by active glaciers. Most of its peaks are under 4000 m, but Mt. McKinley reaches 6194 m. Triangular facets are prominently displayed along the scarp face at interfluves. Volcanic rocks make up much of the Wrangell Mountains to the southeast.