Outer Layer & Rock
What is Earth's outer layer made of underneath both the soil on land and the water in the ocean?
Hard, solid rock.
Matching fossils of Lystrosaurus and Cynognathus (land creatures that could not swim) were found on continents separated by oceans. What explains how they got so far apart?
The continents are on different plates that slowly moved apart as soft rock was added to plate edges over millions of years.
What type of scientific diagram shows a cut-open side view to reveal what the inside of an object looks like?
A cross section.
What is a convergent boundary?
a boundary where two tectonic plates move toward each other.
If geologists drill down under Saudi Arabia (land) or the Arabian Sea (ocean), where will they find hard, solid rock?
Under both places, because Earth's entire outer layer is made of hard, solid rock.
Identical rock formations formed at the exact same time were found in Brazil and South Africa. How did these rocks end up thousands of miles apart?
The plates slowly moved apart as soft, solid rock from underneath was added to the edges of the plates over millions of years.
When looking at a world map of volcanoes and earthquakes, what spatial pattern do they show?
Volcanic activity and earthquakes happen in similar areas along plate boundaries.
What is a transform boundary?
the type of boundary where two plates slide past each other horizontally.
What kind of material lies directly underneath Earth's hard outer plates?
Soft, solid rock that can slowly move and flow.
How long does it take for tectonic plates to separate continents across an ocean?
Millions of years (geologic time)
If you cut an apple or a potted plant vertically down the middle, what view of the object are you looking at?
A vertical cross section.
What is subduction?
This process occurs at convergent boundaries when a dense oceanic plate slides beneath a lighter continental or oceanic plate.
If a team of engineers drills into the seabed of the Indian Ocean and on the island of Sri Lanka, where will they find hard, solid rock?
Under both locations, because Earth's entire outer layer is made of hard, solid rock underneath both land continents and oceans.
Fossil remains of Cynognathus were discovered in Argentina and South Africa. Since Cynognathus lived only on land and could not swim, what process explains their distribution?
Argentina and South Africa are parts of different plates that slowly moved apart as soft, solid rock from underneath got added to the edges of the plates over millions of years.
Looking at geographic maps of active volcanoes and earthquakes around regions like North America or Southeast Asia, what do the symbols reveal about where these events take place?
Volcanic activity and earthquakes are not random; they happen in similar geographic areas along plate boundaries.
When two plates move toward each other at a convergent boundary, what happens to the plate that goes underneath?
It sinks into the soft, solid rock below.
Why is it incorrect to say that Earth's outer layer under the ocean is made of sand or water, or that ocean water fills gaps between separating plates?
Earth's outer layer is made entirely of hard, solid rock everywhere. When plates separate, soft, solid rock from underneath rises and hardens to form new solid rock on plate edges rather than leaving gaps filled by sand or water.
Explain how a geologist can use identical land-dwelling fossils found on two separate continents to argue that the continents were once touching, and describe how they moved apart.
Since the organisms lived in only one land area and could not swim across oceans, the continents had to be touching. They separated as the underlying tectonic plates slowly moved apart over millions of years while soft, solid rock rose and added rock to the plate edges.
What does a vertical cross section of an object like an apple or a potted plant show that an outside photograph cannot?
It shows a cut-open side view revealing the internal structures—such as the seeds and core of an apple or the root network inside a pot—rather than just the outer surface.
A student is worried that two continents moving toward each other across an ocean are going to crash together. How would you explain what actually happens as they move toward each other?
Continents move slowly over millions of years, and as they move together, one plate slowly goes underneath the other plate and sinks into the soft, solid rock below rather than crashing abruptly.