You are probably wondering about how hot is lava. Well you're just about to find out because I'm going to tell you. The Hawaiian lava, (which seem to be at the hot end range) when they erupt they are probably around 1170 to 1175 degrees Celsius. That adds up to about 2140 degrees Fahrenheit. The lava at other volcanoes like St. Helen's is a lot cooler. It is about 100-200 centigrade degrees cooler. That is the main reason why Mount St. Helen's seems so more viscous.
Lava is formed about 150 and 50 km down in the earth. We call it magma before it reaches the surface. Magma is the same thing as Lava.
Lava can travel pretty fast sometimes. In the Mauna Loa eruption in 1950 it flowed 10 kilometers per hour through a thick forest! Once the lava flows become established and good channels developed, the lava in the channels was going at more like 60 km/per hour! Mauna Loa in 1859 (the longest resent Hawaiian flow), was 51 km long. On Mars and Venus lava flows are hundreds of km long!
Pahoehoe lava (the glassy smooth type) will support your weight after only 5-10 minutes since it stops moving. It would still be uncomfortable and hot, and probably might melt your boots, but if you had to get across a flow you could.
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