SEAFLOOR SPREADING

1
SEAFLOOR SPREADING
B40b

• Atlantic Getting Bigger

2
SEAFLOOR SPREADING

• Idea that the ocean bottom is getting larger.
• Atlantic Ocean
• Proposed by Harry Hess
• Evidence in rocks on ocean floor.

3
MID-ATLANTIC RIDGE

• mid-ocean ridge
• found running down center of Atlantic Ocean
• series of mountains on either side

4
ROCK AGES

• 1 - youngest rocks nearest the ridge
• oldest rocks next to continents
• identical pattern on both sides
• THEREFORE new rocks are forming

(B3, Figure 9)
5

• 2 - oldest rocks on ocean floor 200 million
  years old
• oldest rocks on continents 4.6 billion years
  old
• THEREFORE new rocks are forming

(B3, Figure 9)
6
MAGNETIC REVERSAL INDICATORS

• rocks on ocean bottom reflect earths
  magnetic reversals
• THEREFORE new rocks are forming

(B3, Figure 10)
7
ASSIGNMENT

• Draw a section of the ocean floor and mantle
  flanking the mid-Atlantic ridge.
• Use different colors to represent different rock
  ages.
• Label mid-Atlantic ridge and direction of plate
  movement.