a storm
no not always, it can hit trees and buildings, too
If lightning strikes sand, glass is formed.
It is actually both. Here are details from from NSSL http://www.nssl.noaa.gov/faq/faq_ltg.php
When lightning strikes the ground, it creates Clinkers. These are carbon deposits similar to glass that form the structure of a tree, with loads of branches spliting off from the main trunk. The...
RUN!