A massive wildfire near Yosemite National Park is threatening to disrupt San Francisco’s water and power supply and to damage two groves of giant sequoias, Fox News reports. The cause of the fire is not yet known, but it started before the lightening storms that sparked numerous smaller fires across the state. The Rim Fire in San Francisco The Rim Fire, as it’s being called, has forced authorities to mobilize more than a dozen helicopters and half as many fixed wing tankers to drop water and other fire suppressants to aid the 2,800 firefighters working on the ground. “This fire…