Week 6 - Lava Beds national Monument

In researching areas in California, I was interested by the Lava Beds National Monument.  Interesting enough I have never heard of this national monument before visiting the California website and I was interested.

In Lava Bed National Monument, has a series of 20 caves that people can explore.  Some of the caves can be up to 3 miles in length.   These caves were created by lava flow between 10,500 and 65,000 years ago.   As the Lava cooled they created caves call Lava tubes. 

The questions that come up when thinking about lava tubes are:

How does the Lava burn a hole in the rock underground without melting everything in the surrounding area?  and without the rock above it collapsing and melting?    Does the tunnels look burned or melted around the edges that shows the history of the lava flowing?  Now that these lava tubes have turned into caves many of them have stalactites and stalagmites.  How are these created in these caves over thousands of years?
Also, on the website it discusses all the bats that live in the caves in this area and the protection of the bats.  Have bats always lived in caves or as we have become more populated have they moved to these more protected areas?
Sounds like a place I would be interested in visiting in the future.