"The dead trees that fell into the large mountain lake over the years have floated to its outlet. There they have accumulated because the outlet is too narrow for logs to pass through. Water flowing out of the lake must flow through the cracks and gaps between these logs. The water can flow through but sticks get stuck in the gaps. This narrows the gaps enough for twigs to get stuck. They narrow the gaps enough for pine needles, seeds, and insect bodies to get stuck. The log jam strains out floating things which help form a dam oozing water its entire length."
"This dam detains many acre-feet of the Spring meltoff.If not detained, this water would have converged with the meltoff of other streams, swelling the erosive power downstream." 
"After the surge of meltoff subsides, the water detained by the dam oozes through and the dam dries out."

 
The white "bathtub ring" marks on the tree to the right are from pine pollen floating on the lake, marking the high water mark. This helps one realize how much water the log jam dam held back during the peak of Spring runoff. 
"While examining the dried out dam, I realized that all the floating things it had strained out were creations of life. Before life appeared on this planet, the only things that floated were ice and some airy lavas. Now, things that float are so common that I take them for granted, not realizing how unusual is each floating leaf, twig, and seed." (Page 128)

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