FYFD

Tag: stalagmites

  • Puddle Depth Matters for Stalagmites

    Puddle Depth Matters for Stalagmites

    In a cave, mineral-rich water drips from the ceiling, spreading ions used to build stalagmites. A recent study considers how the depth of a pool affects the droplet’s splash and how material from the droplet spreads. The authors found several scenarios that vary widely depending on pool depth.

    A droplet falling into a shallow pool creates a splash that quickly breaks up into droplets. This flings the red droplet material in many directions.
    A droplet falling into a shallow pool creates a splash that quickly breaks up into droplets. This flings the red droplet material in many directions.

    A drop falling into a shallow pool had a splash that quickly broke up into droplets (above). By dyeing the pool green and the droplet red, they could track where the droplet’s material wound up. The spray of small droplets carried fluid far, but the main point of impact had a strong concentration of the drop’s fluid.

    With a deeper pool, the drop's impact creates a thick crown splash that collapses in on itself. The drop's fluid is quickly mixed into the pool.
    With a deeper pool, the drop’s impact creates a thick crown splash that collapses in on itself. The drop’s fluid is quickly mixed into the pool.

    In contrast, a deeper pool sent up a thick-walled splash crown that collapsed in on itself. This droplet’s material saw lots of mixing with the pool, but only near the point of impact. From their work, the authors concluded that models of stalagmite growth should incorporate pool depth in order to capture how minerals actually concentrate and move. (Image credit: cave – H. Roberson, others – J. Parmentier et al.; research credit: J. Parmentier et al.; via APS Physics; submitted by Kam-Yung Soh)

  • Falling Drops and Forming Stalagmites

    Falling Drops and Forming Stalagmites

    The vast stalactites and stalagmites found in caves take millennia to form. Mineral-rich water seeps down the icicle-like stalactites and then drips onto stalagmites below, each drop depositing a little more calcite onto the growing rock. By observing this dripping action first-hand, researchers found that most falling drops create a splash that’s much smaller than the width of the stalagmite they fall onto. So how do stalagmites end up so wide?

    It turns out that there’s a large variance in where drops hit the stalagmite. There’s no wind in these caves to push the droplets, so researchers concluded the drop’s trajectory depends on the vortices it sheds as it falls. A drop that falls from a short height will have a vertical trajectory. But once the drop is falling tens of meters, it can end up as many as several centimeters to the side of where it would fall in a vacuum. This scatter-shot variation in drop impacts is what enables stalagmites to grow so wide. (Image and research credit: J. Parmentier et al., source; via NYTimes; submitted by Kam-Yung Soh)