1. What two great American cities are destined to merge?
Answer
The San Andreas fault, which runs north-south, is slipping at a rate of about 2 inches (5 centimeters) per year, causing Los Angeles to move towards San Francisco. Scientists forecast LA will be a suburb of the City by the Bay in about 15 million years.

2. Can rocks float?
Answer
In a volcanic eruption , the violent separation of gas from lava produces a "frothy" rock called pumice, loaded with gas bubbles. Some of it can float, geologists say. I've never seen this happen, and I'm thankful for that.

Answers to last week's Quiz
Quiz 1: b
Quiz 2: a