June 30

On June 30, 1864, President Abraham Lincoln signed legislation granting Yosemite Valley and the Mariposa Grove to the state of California. This landmark act ensured the protection of these natural wonders for public benefit. It was one of the earliest instances of land conservation by the U.S. government. Lincoln’s decision set a precedent for the national park movement that would follow. The gesture reflected growing appreciation for preserving America’s wilderness.

On June 30, 1908, a powerful explosion occurred near the Tunguska River in eastern Siberia, releasing energy estimated to be hundreds of times greater than the atomic bomb dropped on Hiroshima. Researchers believe the blast was caused by a meteoroid or comet fragment exploding in the atmosphere at an altitude of 5 to 10 kilometers. The resulting shockwave flattened over 2,000 square kilometers of taiga forest and generated seismic waves detected thousands of kilometers away. Surprisingly, the remote location meant few human casualties, and eyewitness accounts were scarce and often secondhand. The event spurred decades of scientific investigation into near Earth objects and impact hazards. Modern studies of tree ring data, soil samples, and atmospheric emissions continue to shed light on the event's true nature. The Tunguska Event remains one of the most dramatic natural phenomena ever recorded.