When lava flows down a volcano, the outside of the lava cools and hardens into rock while the lava underneath continues to flow. If the liquid lava then drains away before hardening, a hollow tube is formed.
|
|
|
|
| |
|
|
|
|
|
|
| Light in the Darkness When lava flows down a volcano, the outside of the lava cools and hardens into rock while the lava underneath continues to flow. If the liquid lava then drains away before hardening, a hollow tube is formed. |
| |
|
|