<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>Animats</author><text>There are mine communication devices that can punch a signal through a few hundred meters of solid rock.  Here&amp;#x27;s a simple one.[1]  VLF can get through, with enough power, a simple signal, and a smart receiver.[2]&lt;p&gt;There&amp;#x27;s been a lot of work on &amp;quot;down-hole communication&amp;quot; for oil and gas drilling.  Modern drilling involves com links to the sharp end, with info coming up and commands going down. Some of the techniques work through the drill string, but some are VLF radios.&lt;p&gt;There are also high-powered ultrasonic pingers, with a range of several kilometers in water.[3]&lt;p&gt;If you could get info for the first kilometer or two, you&amp;#x27;d at least know where to look for the rest of the path.&lt;p&gt;[1] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;radiolocation.tripod.com&amp;#x2F;&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;radiolocation.tripod.com&amp;#x2F;&lt;/a&gt;
[2] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;onlinelibrary.wiley.com&amp;#x2F;doi&amp;#x2F;10.1029&amp;#x2F;2010RS004378&amp;#x2F;full&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;onlinelibrary.wiley.com&amp;#x2F;doi&amp;#x2F;10.1029&amp;#x2F;2010RS004378&amp;#x2F;full&lt;/a&gt;
[3] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;www.sonotronics.com&amp;#x2F;?page_id=96&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;www.sonotronics.com&amp;#x2F;?page_id=96&lt;/a&gt;</text><parent_chain></parent_chain></comment><story><title>The Mystery of Devil&apos;s Kettle Falls</title><url>http://www.mnn.com/lifestyle/eco-tourism/stories/the-mystery-of-devils-kettle-falls</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>cossatot</author><text>For the record lava tubes can happen in flood basalts; I&amp;#x27;ve been to some at Hell&amp;#x27;s Half Acre in Idaho, and I&amp;#x27;m sure there are others. But these are not like karst-type cave systems; they&amp;#x27;re much shorter.&lt;p&gt;It&amp;#x27;s really unlikely that the water goes anywhere other than the lake.  It just might travel through a fracture network and seep out of the lake bottom miles away, but groundwater tends to flow broadly following the topographic slope (driven by the gravitational loading of groundwater surface called the &amp;#x27;hydraulic head&amp;#x27;) and there typically aren&amp;#x27;t isolated tunnels where some water can flow unimpeded by regional groundwater flow.</text><parent_chain></parent_chain></comment><story><title>The Mystery of Devil&apos;s Kettle Falls</title><url>http://www.mnn.com/lifestyle/eco-tourism/stories/the-mystery-of-devils-kettle-falls</url></story>