Today we wrap up the first half of our series on physical geography by taking a closer look at natural hazards - which are physical processes like heat waves and cyclones, earthquakes and volcanic eruptions, and floods and droughts. And when these natural events cause significant harm to humans, we call them natural disasters. So today we'll explore the ways geographers analyze and track these events, and take a closer look at the human impact of Hurricane Katrina in New Orleans and The Boxing Day Tsunami on the Andaman and Nicobar islands.