A swarm of 21 earthquakes jolted the Bay Area early Monday morning, according to data from the U.S. Geological Survey.
The biggest quake of the morning, a 4.2 magnitude temblor, struck just after 7 a.m. southeast of San Ramon, with acute rumbling being felt across areas that included Oakland, Richmond, San Leandro and Hayward.
In San Francisco, residents reported windows rattling in Glen Park and rumbling in Nopa…