Studying the Ocean Floor
What device do scientists use to measure ocean depth?
Echo sounder
Name one major feature discovered on the ocean floor.
Mid-ocean ridges or ocean trenches.
What do isochron maps show?
Areas of the ocean floor with the same age
In what decade was seafloor spreading discovered?
1960s
What happens to continents as the seafloor spreads?
They move with it
Why do scientists use sound waves instead of light to study the ocean floor?
Light can’t travel well in deep, dark water; sound travels farther
Who is one of the first scientists to discover mid-ocean ridges?
Marie Tharp
Where is the youngest oceanic crust found?
Near mid-ocean ridges.
Seafloor spreading helps explain what three things?
Ocean floor features, seafloor ages, and continental drift
What theory does seafloor spreading support?
Wegener’s continental drift theory.
The longer it takes for a sound wave to return, the ______ the ocean is.
Deeper
What are ocean trenches?
Deep underwater valleys where crust is destroyed.
Where is the oldest oceanic crust found?
Near ocean trenches.
What rises through cracks at mid-ocean ridges to form new crust?
Magma
Why don’t continents just push through the ocean floor?
They move along with the spreading crust, not through it.
What does the phrase mowing the lawn mean when mapping out the ocean floor?
To go back and forth near the same grid point scanning.
What is the deepest part of the ocean?
Mariana Trench
What pattern do seafloor ages form around mid-ocean ridges?
Mirror-image stripes on both sides of the ridge
What is the difference between magma and lava?
Magma is underground; lava is magma that has reached the surface.
What layer of the Earth do continents NOT move through?
The solid mantle
What is created using data from echo sounders?
Topographic maps of the ocean floor.
What are mid-ocean ridges?
Underwater mountain ranges
If you are standing on very old seafloor, are you closer to a ridge or trench?
Ocean trench
Why is the seafloor called a “conveyor belt”?
Because new crust forms at ridges and old crust is destroyed at trenches in a continuous process
What is the main reason scientists know continents are moving?
Evidence from seafloor spreading and matching age patterns on both sides of ridges.