Fall line

<p>A fall line (or fall zone) is the area where an upland region and a <a href="/facts/Coastal_plain/5lx4pTgr">coastal plain</a> meet and is noticeable especially the place rivers cross it, with resulting <a href="/facts/Rapids/VE1IfXCE">rapids</a> or <a href="/facts/Waterfall/CDyaLQIQ">waterfalls</a>. The uplands are relatively hard <a href="/facts/Basement_(geology)/nThFlUPv">crystalline basement rock</a>, and the <a href="/facts/Coastal_plain/5lx4pTgr">coastal plain</a> is softer <a href="/facts/Sedimentary_rock/HQDCjrco">sedimentary rock</a>. A fall line often will recede upstream as a river cuts out the uphill dense material, forming "c"-shaped waterfalls and exposing bedrock <a href="/facts/Shoals/uVP4nYGo">shoals</a>. Due to these features, riverboats typically cannot travel any further inland without <a href="/facts/Portage/Fen64Sjx">portaging</a>, unless <a href="/facts/Lock_(water_navigation)/rFGHXS0p">locks</a> are built. The rapid change of elevation of the water and resulting energy release make the fall line a good location for <a href="/facts/Water_mill/UTvzQY8S">water mills</a>, <a href="/facts/Grist_mill/TP4qMmSr">grist mills</a>, and <a href="/facts/Sawmill/16NUH5RC">sawmills</a>. Seeking a <a href="/facts/Head_of_navigation/EaScb9eE">head of navigation</a> with a ready supply of water power, people have long made settlements where rivers cross a fall line.
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Fall line open-in-new

Fall line