When basalt lava is chilled rapidly in the water in an ocean or ...

[jerry coleman]

When basalt lava is chilled rapidly in the water in an ocean or lake, it forms bulbous structures called
  ___________________ _. Fill in the blank(s) with the appropriate word(s).

Question 2

Besides monitoring, what other knowledge helps geologists determine what to expect for eruptions
  from a given volcano? What will be an ideal response?

[daiying98]

Answer to Question 1

pillow lava

Answer to Question 2

Knowledge about the past history of the volcano.