Main <a href="https://en.wikipedia.org/wiki/Barton_Springs" class="extiw" title="en:Barton Springs">Barton Spring</a> in <a href="https://en.wikipedia.org/wiki/Austin" class="extiw" title="en:Austin">Austin</a>, <a href="https://en.wikipedia.org/wiki/Texas" class="extiw" title="en:Texas">Texas</a>, a prominent fracture (visible here) in <a href="https://en.wikipedia.org/wiki/Limestone" class="extiw" title="en:Limestone">limestone</a> rock. Through this <a href="https://en.wikipedia.org/wiki/Artesian_aquifer" class="extiw" title="en:Artesian aquifer">artesian</a> <a href="https://en.wikipedia.org/wiki/Karst_topography" class="extiw" title="en:Karst topography">karst spring</a> water emerges to the surface from the karstic <a href="https://en.wikipedia.org/wiki/Edwards_Aquifer" class="extiw" title="en:Edwards Aquifer">Edwards Aquifer</a>. This spring is situated near the diving board in <a href="https://en.wikipedia.org/wiki/Barton_Springs_Pool" class="extiw" title="en:Barton Springs Pool">Barton Springs Pool</a>. Photo provided by US Geological Survey.
USGS
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USGS