Science Test 2026

Wegener’s 1st piece of evidence

Rock formations- similar rocks found on opposite sides of the Atlantic ocean (Appalachian + Caledonian Mountains)

Wegener’s 2nd piece of evidence

Fossil evidence- found fossils of land reptiles on opposite sides of the ocean… How did they get across if they can’t swim? Land areas must have been connected at one time for land reptiles to cross

Wegener’s 3rd piece of evidence

Climate evidence- found remnants of glaciers in regions that are warmer today… found near the South Pole and “drifted” away

What did early cartographers realize, which supported Continental Drift?

They noticed that the continents seemed to fit together like a puzzle.

Why wasn’t Wegener’s hypothesis supported at first?

Wegener couldn’t explain how the continents were moving through solid ocean crust and what could have been pushing the continents.

Who is Harry Hess?

Harry Hess (1960s) used sonar to map the bottom of the ocean.

How did sonar help support the theory of seafloor spreading?

The mapping determined that the ocean floor was NOT flat. They found giant underwater ridges (mountains) and trenches. Seafloor spreading created these ridges and trenches.

1st piece of evidence to support seafloor spreading

Age of ocean crust- isochron maps showed that rock is younger near the ridge and rock is older near the trenches.

2nd piece of evidence to support seafloor spreading

Magnetic symmetry on both sides of ridge- *North and South Pole* When Earth’s magnetic field switches direction, a record is kept in the magnetic rocks of the seafloor… symmetrical pattern is evidence of seafloor spreading; Reversed Polarity: magnetic field points South, Normal Polarity: magnetic field points North

Prior to the mid-1900s, what did people think the seafloor looked like?

Many people thought the seafloor was flat.

What is the difference between an ocean ridge and an ocean trench?

Ocean ridges are fairly shallow and form when tectonic plates move away from each other (divergent). Ocean trenches are very deep and form when tectonic plates push into each other and one plate subducts under the other (more dense goes under) (convergent subduction).

What type of boundary new crust form at? What type of plate boundary does old crust get destroyed at?

New crust forms at oceanic-oceanic divergent plate boundaries and old crust gets destroyed at continental-continental divergent plate boundaries.

Compare and contrast continental and oceanic crust

Oceanic crust is denser, younger, and made of basalt. Continental crust is thicker, older, and made of granite.

Describe what happens at an oceanic-continental plate boundary

Two oceanic plates push into each other and the more dense plate subducts underneath the other plate, forming a deep-sea trench and volcanic mountains.

Describe how the Himalayan Mountains formed.

Two continental plates push against each other and push up the crust, forming the mountains. No subduction occurs!

What forms at convergent plate boundaries?

Deep-sea trenches, volcanic mountains, large mountains

What forms at divergent plate boundaries?

New ocean crust, rift valleys

What forms at transform plate boundaries?

Earthquakes

What is the formula for density?

m/v=d

Lithosphere

The solid layer of the Earth that consists of the crust and the rigid upper part of the mantle.

Asthenosphere

The plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move above it.

Outer Core

The layer below the mantle and made of iron and nickel.

Inner Core

The solid, dense center of the Earth, made of iron and nickel.

Mantle

The layer between the crust and the outer core.

Crust

The outermost layer of Earth composed of two types: continental and oceanic.

What are volcanic hot spots?

Unusually hot regions of Earth’s mantle where magma rises and breaks through crust.

Explain how the islands of Hawaii formed

As the pacific plate moves NW over a hot spot, every time the hot spot has a volcanic eruption, the hot magma hardens, beginning to form a Hawaiian island.

What is the difference between convergent and divergent volcanism?

Convergent- mostly Ring of Fire (along islands + coastlines)

Divergent- mostly underwater at mid-ocean ridges, or at continental rifts

Describe the motion of a P-wave

P-waves squeeze and push rocks in the same direction the waves are traveling. P-waves are the fastest waves and travel through liquids and solids.

Describe the motion of an S-wave

S-waves move up and down with the direction of the wave. S-waves arrive second, after P-waves, are slower, and only travel through solids.

Which seismic wave is most destructive and why?

Surface waves are the most destructive because they cause the most movement on the ground and they take the longest time to pass.

What is the difference between the focus point and the epicenter?

The focus is where the body wave originates and the epicenter is right above the focus, where the surface waves originate.