🪨 Balcones Escarpment: The Step That Sited the Towns

What you’ll learn

1. See the stepRecognize the Balcones Escarpment as the surface expression of a broad, east-downthrown fault zone.The landscape looks like a step because many faults combine to make one long boundary.
2. Read the two sidesCompare the thin-soil Edwards Plateau with the deeper-soil Blackland Prairie.The fault zone helps explain why hills and ranch country meet flatter, cultivated prairie.
3. Follow the waterExplain how fractured limestone moves water from streams to springs.The same rock that swallows streamflow can return it through large springs.
4. Live with the seamConnect the Edwards aquifer and Flash Flood Alley to everyday risk and water supply.The seam gives towns dependable groundwater and exposes them to fast runoff and floods.

Questions this course answers

Grounded in trusted sources

• Handbook of Texas Online — Balcones Escarpment (fault zone several miles wide, downthrown east; ~1,000 ft near Del Rio, ~300 ft San Antonio to Austin; artesian springs; Hill 1890)
• Handbook of Texas Online — Hill, Robert Thomas (delineated and named the Balcones fault zone; described it in 1890)
• Handbook of Texas Online — Comal Springs (largest in Texas; average ~9,000 L/s, 1892–1978); San Marcos Springs (second largest; ~4,300 L/s, 1892–1978); Barton Springs (fourth largest; ~370 gal/s, 1895–1978)
• U.S. Geological Survey — Karst Aquifers: Edwards Balcones Fault Zone Aquifer (most transmissive aquifer in Texas and Oklahoma; EPA sole-source; primary water for San Antonio; streams lose flow across the fault zone)
• Texas Water Resources Institute / Texas A&M AgriLife — Do you live in Flash Flood Alley? (2016): alley follows the Balcones from Waco south to Uvalde; Thrall 38.2 in., 9–10 Sept. 1921
• Handbook of Texas Online — Edwards Plateau (thin soil over Comanchean limestone; southernmost Great Plains unit; grazing country)

Every Wunder lesson is built from real, reputable sources — never invented.

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