Seafloor spreading at midoceanic ridges is how scientists first discovered the periodic reversal of what?

More Questions:

What Beatrix Potter character has roasted grasshopper for supper after failing to catch minnows?

What two characters are sculpted on Hannibal, Missouri's Main Street?

What year did Arthur Hailey publish the novel "The Moneychangers"?

Which US state is nickname the "Palmetto State"?

Which gas has the characteristic smell of rotten eggs?

The "K" in vitamin K stands for the Danish spelling of what eleven-letter word?

How many episodes of "The Cosby Show" were made?

Who played the character of Paul Bratter in the 1967 film "Barefoot in the Park"?

Which singer was born Katheryn Elizabeth Hudson?

What 1980s movie soundtrack gave us the #1 hit by the band Berlin entitled "Take My Breath Away"?

How many points did the Dow drop on "Black Monday" in 1987?

What 20 year old boxer became the youngest WBL heavyweight champ in History, when he beat Trevor Berbick in 1986?

Which English band had the hit song "Unbelievable"?

Which major river is adjacent to Memphis, Egypt?

Lome is the capital of which country?