Abstract Urbanization is a major process now shaping the environment. This field trip looks at the hydrogeology of the general Washington, D.C., area and focuses on the city’s lost springs. Until 150 years ago, springs and shallow dug wells were the main source of drinking water for residents of Washington, D.C. Celebrating the nation’s bicentennial, Garnett P. Williams of the U.S. Geological Survey examined changes in water supply and water courses since 1776. He examined old newspaper files to determine the location of the city’s springs. This field trip visits sites of some of these springs (few of which are now flowing), discusses the hydrologic impacts of urbanization and the general geological setting, and finishes with the Baltimore Long Term Ecological Research site at Dead Run and its findings. The field trip visits some familiar locations in the Washington, D.C., area, and gives insights into their often hidden hydrologic past and present.

Abstract Welcome to the Appalachian landscape! Our field trip begins with a journey across Fall Zone (Fig. 1 ), named for the falls and rapids on streams flowing from the consolidated rocks of the Appalachians onto the unconsolidated sediments of the Coastal Plain. The eastern U.S. urban centers are aligned along the Fall Zone, the upstream limit of navigation. Typically, the rocks west of the Fall Zone are part of the Piedmont province. This province exposes the metamorphic core of the Appalachian Mountains exhumed by both tectonics and erosion. At least four major phases of deformation are preserved in Piedmont rocks, three Paleozoic convergent events that closed Iapetus, followed by Mesozoic extension that opened the Atlantic Ocean. A record of Cretaceous to Quaternary exhumation of the Appalachians is preserved as Coastal Plain sediments. Late Triassic and Jurassic erosion is preserved in the syn-extensional fault basins, such as the Newark basin, or is buried beneath Coastal Plain sediments (Fig. 1 ). The trip proceeds northwest across the Fall Zone and Piedmont and into the Newark basin. Late Triassic and Jurassic fluvial red sandstone, lacustrine gray shale, and black basalt were deposited in this basin. The Newark basin is separated from the Blue Ridge by a down to the east normal fault that locally has contemporary microseismicity. The Blue Ridge represents a great thrust sheet that was emplaced from the southeast during the Alleghenian orogeny (Permian). The summits of the Blue Ridge are commonly broad and accordant. Davis (1889) projected that accordance westward to the summits of the Ridge and Valley to define his highest and oldest peneplain—the Schooley peneplain. North and west of the Blue Ridge is the Great Valley Section of the Ridge and Valley Province (Fig. 1 ). Where we cross the Great Valley at Harrisburg, it is called the Cumberland and Lebanon valleys. This section is underlain by lower Paleozoic carbonate, shale, and slate folded and faulted during the lower Paleozoic Taconic orogeny. The prominent ridge on the west flank of the Great Valley is Blue or Kittatinny Ridge. It is the first ridge of the Ridge and Valley Province; the folded and faulted sedimentary rocks of the Appalachian foreland basin, deformed during the Alleghenian orogeny. Drainage during most of the Paleozoic was to the northwest, bringing detritus into the Appalachian foreland basin. The drainage reversed with the opening of the Atlantic Ocean and southeast-flowing streams established courses transverse to the strike of resistant rocks, like the Silurian Tuscarora Sandstone holding up Blue Mountain. West and north of the Ridge and Valley is the Allegheny Plateau, that part of the Appalachian foreland that was only gently deformed during Alleghenian shortening. Our trip will traverse that part of the plateau called the Pocono Plateau which is underlain by Devonian to Penn-sylvanian sandstone. At the conclusion of our trip, we will reverse our transverse of the Appalachians by traveling from the Pocono Plateau to the Ridge and Valley, to the Great Valley, to the Newark Basin, to the Piedmont, and then to one of the great Fall Zone cities—Philadelphia—via the Lehigh and Schuylkill rivers.

Abstract Subsurface water affects near-surface processes and landforms in a wide variety of ways. Its essential role in weathering, soil development, slope failure, and karst topography has long been acknowledged. However, its importance in other aspects of the development of landforms has just begun to be recognized in the last decade or so. In this chapter we discuss some major aspects of ground-water geomorphology and ways in which subsurface water can shape the Earth’s surface. In the next chapter, D. C. Ford, A. N. Palmer, and W. B. White discuss the special conditions of karst landforms; in this chapter we discuss other aspects of the role of underground water in landform development. This chapter is organized as follows: first, some effects of water in the vadose or unsaturated zone above the water table, with emphasis on weathering and soil development and their influence on landscape (by Pavich), mass wasting and slope failure (Dietrich and Rogers), and hillslope hydrology (Dunne), with its influence on piping and pseudokarst (Parker) and on development of hillslopes and gully heads (Higgins). Next, the role of water in the saturated zone at or beneath the water table, and its effects on permafrost and pseudokarst (Sloan), land subsidence (Péwé), spring sapping and valley network development (Baker), submarine landforms (Robb), sea cliffs (Norris), scarp retreat (Higgins), and surface stream channels (Keller). Finally, ways are considered in which regional geomorphology can control groundwater behavior and hydrology (Coates).