How Hot Does It Get? (Grades 7-8)

Common questions in the coastal area of the park are "How hot is the water at the lava entry into the ocean?" and "How hot is the lava as it pours out of the lava tube?" Geologists measure the temperature of geologic materials in degrees Celsius (C). This scale is very convenient because water freezes at 0C and boils at 100 C at sea level.

Most American students learn to measure temperatures using the Fahrenheit scale. This scale is a bit confusing, since water freezes at 32 F and boils at 212 F at sea level. Activity 8 helps students become familiar with the Celsius scale and learn a bit about the eruption. The students need the following equations. To convert degrees Celsius to degrees Fahrenheit, use this equation:

			 F = (C x 9/5) + 32  
If students keep in mind that 0 C is equal to 32 F, they may remember that 32 is added to the Celsius temperature. To convert degrees Fahrenheit to degrees Celsius, use this equation:

			 C = (F - 32) x 5/9  
Students can check the equation by remembering that 100 C = (212 F - 32) x 5/9. Use the equations to answer these questions.

Click here for the handout for this activity.


  1. Lava pouring out of the lava tube is about 1150 C. How hot is the lava in F? 2,100 F.

  2. Steam generated at the interface between lava and water is estimated to be 135 C. How hot is the steam in F? 275 F

  3. The maximum water temperature measured in front of the lava entry was 70 C. How hot is the water in F? Could you go for a comfortable swim in this water? Hint: Convert your body temperature (98 F) to C and compare to the water temperature. Your body temperature is about 36 C. If you fell into 70 C water, it would burn you.

  4. About 60 feet (200 m) offshore, the water that was heated by the lava has been diluted by colder ocean water, and temperatures are typically 36 C. Could you go for a comfortable swim in this water? Yes. This temperature is equivalent to about 97 F, about the temperature of a hot tub. Note that a swim in front of the lava entry would be a dangerous excursion. Not only is the lava dangerous; but so are the currents, surf, and bench collapses.

  5. Tephra from the Puu Oo high fountains glowed yellow and orange. These colors indicate a temperature of about 1000 C. What was the temperature of the lava fountain in F?

  6. On some days, rangers take visitors out to see cooling lava flows. The flows typically have cracks in a thick, black crust. Deep in the cracks, the lava still glows red. The temperature of the red lava beneath the crust is about 500 C. What is the temperature of the red lava in F? 930 F.

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