The Mystery of Horseshoe Lake

Near the town of Mammoth Lakes, California are a number of lakes each with their own points of interest. One of them, Horseshoe Lake, caused a stir in 1990 when areas of trees near the lake started dying and no one knew why. So on a 2013 trip to the area we decided to check it out.

On the way to Horseshoe Lake is a must stop at the Twin Falls Overlook with views of Twin Lakes in the valley below.

It is a popular place to take pictures and enjoy the view.

Even at an and altitude of 8,600 feet Twin Lakes is the lowest lake in the Lakes Basin and the
only one accessible by car year-round.

Contrary to its name Twin Lakes is really a single lake with a narrow choke in the middle.

Continuing on to Horseshoe Lake we decided to hike around the lake.

This was a number of years into a drought cycle and the drop in water level is evident here.

The lake does provide some nice views with Mammoth Mountain in the background.

And without the trees on the sides.

A view of Mammoth Rock through the limbs of a downed tree.

Downed trees can also make for a picture posing opportunity.

OK, we made it all the way around the lake so just what is this mystery of Horseshoe Lake?

During 1990 the U.S. Forest Service rangers noticed areas of dead and dying trees between Mammoth Mountain and Horseshoe Lake. Drought and insect infestations were looked at as causes but were eliminated. Then a geologic explanation was suspected and USGS scientists found high concentrations of carbon dioxide (CO2) gas in the soil. While one might think trees like CO2 it turns out their roots need to absorb oxygen (O2) directly. Over time the trees are killed because of the CO2 interfering with the trees nutrient uptake. The CO2 is thought to come from a small body of magma (molten rock) rising beneath the area after numerous small earthquakes occurred the previous year. Now the tree kill totals 170 acres in six general areas one of which is seen here.

McLeod Lake is just a short hike from Horseshoe Lake so on another trip we decided to visit it. Along the trail downed tree roots provided some photo opportunities.

Trees obscured the lake as we approached it.

When we got to the edge of the lake we could see more. The haze is from wildfires. Though none of the fires were close to the Mammoth Lakes area the smoke still found its way here.

The trees made it hard to take a picture of the entire lake so this is the left side.

And the right side.

More Information:

Twin Lakes information

Horseshoe Lake information

McLeod Lake information

U.S. Geological Survey Fact Sheet titled Invisible CO2 Gas Killing Trees at Mammoth Mountain, California