SEA FLOOR SPREADING

SEA FLO

OR SPR

EADING

PL A

TE

TE

CT

ON

I CS

CONTENT GOAL:

To be able to explain sea floor spreading.

BELL WORK 1/29

What process causes plates to move?

SEA FLOOR SPREADING UP CLOSE

SEA FLOOR SPREADING CROSS-SECTION

SEA FLOOR SPREADING AERIAL VIEW

BELL WORK 1/30

Write this down on page 16. Watch video continental Drift song for answers.

1. Who were the two scientists who helped discover continental drift?

2. What technology helped explain sea floor spreading

BELL WORK 1/30 ANSWERS

• Alfred Wegener (pronounced Vay guh nur) proposes continental drift

• 30 years later, Harry Hess , a naval officer, confirms continental drift using sonar

• Soar is the technology that provides the proof for the mechanism of continental drift

SONAR

Sonar = Sound Navigation and Ranging

SONAR

• Used on boats to navigate around objects

• Used by fishermen to find large schools of fish

• Bats and whales use echolocation(like sonar) to communicate, search for prey, and work their way through darkness

MILITARY USES

• WWII to detect U-boats (German Submarines) problems though

• Cold War find nuclear warheads hidden underwater away from satellites and air strikes

HOW SONAR WORKS

• A noise is generated• The time it takes sound to bounce off

an object and return• You can gauge how far away an object

is

TYPES OF SONAR

• Passive – underwater microphone• Active – generate their own sound

waves•Emits a sound•Receiver measures how long it takes for sound wave to return

CALCULATING DEPTH OF SEA FLOOR

D = (T/2)(V)

T = time in secondsV = speed of sound =

5000ft/second

SS SAPONA

• 1926 SS Sapona ,used to transport alcohol during prohibition, ran aground during a hurricane

• Today it sits 54 miles from the beaches of Miami

• How deep is water around SS Sapona if it can still be seen above the water?