How much elevation change to create thermals?

[bigbob]

What kind of elevation change is required to create thermals? 50ft? 100ft? 200ft?

[dan]

it don't take much... I would say 10 or 15 feet, part of it has to do with steepness to though. The smaller the hill the less the effect.. so in flat land a 15 foot elevation might have the best bedding option, but in steeper country, you need to look at the steeper elevation.

[Beason]

Zero change in elevation actually. You ever get the chills when the sun comes up during a cooler morning? All the warm air is rising and you're stuck with the cold air that is more dense and sinks.

The steeper the slope, the more thermal current you should feel generally.

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[bigbob]

Thanks guys that makes sense. My next question is what type of change would be needed to create the tunnels discussed in the hill country dvd? For instance if you had a small ridge (we"ll say 20-50ft) would there be enough of a thermal tunnel on the leeward side to alter deer movement?