Chapter 5 Earth Science 7th Grade

Question 1

J. Tuzo Wilson

Answer 1

He observed that cracks in the continents are similar to those in the ocean floor.

Question 2

Plates

Answer 2

Lithosphere is broken into separate sections. They fit together along cracks in the lithosphere. It carries continents or parts of the ocean floor.

Question 3

Scientific Theory

Answer 3

It is a well tested concept that explains a wide range of observations.

Question 4

Plate Tectonics

Answer 4

It states that pieces of Earth’s lithosphere is in slow constant motion, driven by the convection currents in the ocean. The theory explains the formation, movement, and subduction of Earth’s surface. Geologists think that movement of convection currents in the mantle is the major force that causes plate motion. As the plates move, they collide, pull apart, producing spectacular changes in the Earth’s surface.

Question 5

Faults

Answer 5

It breaks in Earth’s crust where rocks have slipped past each other.

Question 6

Divergent Boundaries

Answer 6

The place where 2 plates move apart from each other. It occurs on land. When it develops on land, 2 of Earth’s plates slide apart.

Question 7

Rift Valley

Answer 7

It is a deep valley that forms along the divergent boundary.

Question 8

Convergent Boundary

Answer 8

The place where 2 plates come together. The result is called a collision. When they collide the density of the plates determines which one is on top. The one that is more dense is the one that sinks.

Question 9

Transform Boundary

Answer 9

The place where 2 plates lip past each other moving in opposite directions.

Question 10

Plate Movements Over Time

Answer 10

Before Pangaea existed, other super continents formed and split apart over billions of years.

Question 11

Plate Boundary

Answer 11

The line where the edges of Earth’s plates meet.

Question 12

Mid-Ocean Ridge

Answer 12

It occurs between plates that are pulling apart. Undersea mountain chain where new ocean floor is, is produced.

Question 13

Sonar

Answer 13

Device that bounces sound waves off underwater objects and then records echoes of those sound waves. Time it takes for the echo to arrive indicates distance to object.

Question 14

Harry Hess

Answer 14

He is an american geologist that examined maps of the mid ocean ridge system. He made a conclusion that Wegener was right

Question 15

Sea Floor Spreading

Answer 15

The sea floor spreads apart along both sides of the mid ocean ridge as new crust is added. The ocean floor is like a conveyor belt. It begins at mid ocean ridge forming a crack along the oceanic crust.

Question 16

Alvin and Evidence from Molten Material

Answer 16

A small submarine, Alvin, was built to withstand the crushing pressures. The crew found strong rocks shaped like pillows. This type of form is only from when molten material hardens quickly after erupting under water.

Question 17

Evidence from Magnetic Stripes

Answer 17

It is strips of magnetic iron that show how Earth’s poles have reversed themselves several times. It last happened 780,000 years ago. If suddenly reversed themselves, your compass needle would point south.

Question 18

Evidence from Drilling Samples

Answer 18

Farther away from the mid ocean ridge the older the rocks were. The youngest rocks where in the center of the mid ocean ridge. This shows that sea floor spreading really has taken place.

Question 19

Deep Ocean Trenches

Answer 19

The ocean floor plunges into deep underwater canyons. The ocean crust bends downwards.

Question 20

Subduction

Answer 20

The process of oceanic crust sinks beneath a deep ocean trench and back into the mantle at the convergent plate boundary. Sea floor spreading and subduction work together.

Question 21

How is heat transferred?

Answer 21

Heat is transferred from the movement of energy from one object to a cooler object.

Question 22

Radiation

Answer 22

The transfer of energy (heat) through open space.

Question 23

Conduction

Answer 23

It is the heat transfer within a material or between materials that are touching.

Question 24

Convection

Answer 24

It is the heat transfer by the movement of currents within a fluid (liquid or gas).

Question 25

Why does the density of a liquid or gas change with temperature?

Answer 25

The particles move faster and faster creating a heated gas or liquid. The density decreases. But when it cools, particles slow down making it cooler and closer together.

Question 26

What causes convection currents?

Answer 26

Heating and cooling of a gas or liquid, changes in the fluid’s density, and the force of gravity combines together to set convection currents in motion.

Question 27

What causes convection currents in Earth’s mantle?

Answer 27

Heat from the core and the mantle itself causes convection currents in the mantle.

Question 28

What did Alfred Wegener do?

Answer 28

He hypothesized that all the continents were once joined together in a single landmass and have since drifted apart.

Question 29

Continental Drift

Answer 29

It is continents moving slowly over Earth’s surface.

Question 30

Pangaea.

Answer 30

It means “all lands” and existed about 300 million years ago. The process slowly started moving to what we have today.

Question 31

Land Feature Evidence That Wegener Used To Support His Idea

Answer 31

He pieced together maps of South America and Africa. He noticed that mountain ranges matched up.

Question 32

Fossil Evidence That Wegener Used To Support His Idea

Answer 32

Glossopteris fossils were found in South America and Africa.

Question 33

Climate Evidence That Wegener Used To Support His Idea

Answer 33

The continents had close weather.

Question 34

Why was Wegener’s theory rejected most geologists of his time?

Answer 34

South Africa was once covered in continental glaciers. South Africa is supposedly known to be mild. Wegener said that South Africa was closer at one point in time. He couldn’t explain the force on how it happened. IT eventually became true.

Question 35

Evidence from Rock Samples

Answer 35

Rocks from inside Earth give geologists clues about Earth’s Structure. Geologists can make inferences about conditions deep inside Earth.

Question 36

Evidence from Seismic Waves

Answer 36

Geologists use an indirect method. When earthquakes occur, they produce seismic waves. Geologists record them and study how they travel through Earth. Earth’s interior is made up of several layers.

Question 37

Seismic Waves

Answer 37

Seismic Waves are vibrations that travel through Earth carrying the energy released during an earthquake.

Question 38

Temperature

Answer 38

The high temperatures inside Earth are the result of heat left over from the formation of Earth. In addition, radioactive substances inside Earth release energy.

Question 39

Pressure

Answer 39

It is the results from force pressing on an area.

Question 40

Earth’s Layers in Order

Answer 40

1. Crust
2. Lithosphere
3. Asthenosphere
4. Lower Mantle
5. Outer Core
6. Inner Core

Question 41

Crust

Answer 41

Hard and rigid, Earth’s outermost and thinnest layer, only a few miles thick under the ocean and averaging 20 miles thick under the continents. The layer of rock that forms outer skin. The layer of solid rock that includes dry land and ocean floor.

Question 42

Lithosphere

Answer 42

Uppermost part of the mantle. “Lithos” means stone in Greek. Made up of crust and a tiny bit of the upper mantle. This layer is divided into several constantly moving plates of solid rock that holds the continents and oceans.

Question 43

Asthenosphere

Answer 43

Plates of lithosphere move on this hot, malleable semi liquid zone in the upper mantle, directly underneath the lithosphere. It is a hot and under increasing pressure, less rigid, soft layer, “asthenes” means weak, and it is still a solid.

Question 44

Lower Mantle

Answer 44

It is solid, extends to the core, and is made up of the metals, iron and nickel.

Question 45

Outer Core

Answer 45

It is the layer of molten metal that surrounds the inner core. It is a liquid. The only liquid layer of the Earth. It is a sea of mostly iron and nickel.

Question 46

Inner Core.

Answer 46

It is a dense ball of solid metal. The intense pressure squeezes atoms of iron and nickel so much that they can not spread out and become a liquid. It is an extremely hot, solid sphere of mostly iron and nickel at the center of the Earth.