Tunguska event
At first, there was no interest in the event. Over a decade after the event, Leonid Kulik, a Russian mineralogist led an expedition to the area. In his expedition of 1921 and 1922, he only got to Kansk, which is  away from the "epicenter" of the event.  In 1927, Kulik reached the region where the event happened, in 1938 he ordered aerial photos be taken.