Plate tectonics lesson 1-4

The earth's inner core state of matter is ____________ and ____________ than the outer core and mantle.

• Liquid, less

• Solid, less

• Liquid, more

• Solid, more

Answer explanation

The earth's inner core is in a solid state due to immense pressure, making it denser and more solid than the outer core and mantle, which are liquid. Thus, the correct answer is 'Solid, more'.

What provides evidence for Earth having a solid core?

• gravity

• seismic waves

• convection currents

• radiation

Answer explanation

Seismic waves provide evidence for Earth's solid core because they travel differently through solid and liquid materials. Their behavior indicates that the inner core is solid, while the outer core is liquid.

Which layer of the Earth is a dense ball of solid iron?

• crust

• mantle

• outer core

• inner core

Answer explanation

The inner core is a dense ball of solid iron, located at the Earth's center. Unlike the outer core, which is liquid, the inner core remains solid due to the immense pressure, making it the correct answer.

What occurs inside the Earth where the inner core heats up another layer and cools as it reaches the Earth’s surface?

• tectonic plates

• convection currents

• conduction

• radiation

Answer explanation

Convection currents occur inside the Earth as the inner core heats the surrounding layers. This heat causes the material to rise, cool as it reaches the surface, and then sink back down, creating a continuous cycle.

Occurs when a plate is pushed/pulled down because it is less dense is called what?

• subduction

• sea-floor spreading

• convection currents

• tectonic plates

Answer explanation

Subduction occurs when a tectonic plate is pushed or pulled down into the mantle due to being less dense than the surrounding material. This process is crucial in plate tectonics and leads to geological phenomena like earthquakes.

Which layer of the Earth is molten (liquid) and is composed of iron and 10% sulfur?

• crust

• mantle

• outer core

• inner core

Answer explanation

The outer core is the layer of the Earth that is molten and composed mainly of iron, along with about 10% sulfur. This distinguishes it from the solid inner core and the solid mantle and crust.

The hypothesis that all the continents were once joined in a single landmass and have since slowly moved apart is known as what?

• Plate tectonics

• continental drift

• pangaea

• convection currents

Answer explanation

The hypothesis that all continents were once joined in a single landmass and have since moved apart is known as continental drift. This concept explains the gradual movement of continents over geological time.

Which device bounces sound waves off underwater objects and then records the echoes of these sounds?

• radar

• GPS

• satellite

• sonar

Answer explanation

The correct answer is sonar, which uses sound waves to detect and locate underwater objects by bouncing sound waves off them and recording the echoes. Radar and GPS are not used underwater, and satellites do not operate in this manner.

What is the name of the longest chain of mountains in the world that are beneath Earth's oceans?

• Grand Canyon

• Sea-floor spreading

• Trenches

• Mid-ocean ridge

Answer explanation

The longest chain of mountains beneath the oceans is called the Mid-ocean ridge. It is a continuous mountain range that encircles the Earth, formed by tectonic plate movements, unlike the other options listed.

Which scientist suggested a process he called sea-floor spreading that continually adds new material to the ocean floor?

• Alfred Wegener

• Marie Tharp

• Harry Hess

• Albert Einstein

Answer explanation

Harry Hess proposed the theory of sea-floor spreading, which explains how new material is continuously added to the ocean floor, supporting the concept of plate tectonics. Alfred Wegener is known for continental drift, not sea-floor spreading.