Unit E Section 3 Introduction Changes in the Earth's Surface
Completion requirements
Section 3: Continents slowly drift and change the Earth's surface.
Unit E: Section 3 - Introduction
Figure E.S.3.1 – What looks very much like a jigsaw puzzle of Earth is actually a map of tectonic plates.
Figure E.S.3.2 – Various natural events occur where Earth’s tectonic plates meet.
The World around Us Changes Constantly
The life we see changes all the time, but the actual Earth stays much the same in our eyes. You might see a bit of erosion in your garden when it rains, or a work crew might dig a hole or drill a well, but that’s about it. Do you know anyone who has seen a mountain appear suddenly, an island move to the other side of the planet, or the ocean floor slip under a continent? These are very challenging events to even imagine let alone observe and measure. Yet, they happen, have been happening for billions of years, and will continue to happen for billions more – probably.
Science has begun only recently to understand what is happening on Earth and how it forms all the amazing natural things we see.
Mountains being built from old seafloors. Volcanic islands rise in the middle of the ocean. Geysers of steam blast through vents from deep underground. Huge cracks in Earth’s crust with slowly moving plates of rock move in different directions on either side. Even entire continents move slowly around Earth’s surface as though they float on the surface of a liquid globe. WOW! Lots of action – but very slow motion!
Most of Earth’s insides are hidden from us. Many of these events have been difficult to understand. As geologists and their equipment become more advanced, sophisticated measurements can be used to support the concepts we use to explain what is happening.
The life we see changes all the time, but the actual Earth stays much the same in our eyes. You might see a bit of erosion in your garden when it rains, or a work crew might dig a hole or drill a well, but that’s about it. Do you know anyone who has seen a mountain appear suddenly, an island move to the other side of the planet, or the ocean floor slip under a continent? These are very challenging events to even imagine let alone observe and measure. Yet, they happen, have been happening for billions of years, and will continue to happen for billions more – probably.
Science has begun only recently to understand what is happening on Earth and how it forms all the amazing natural things we see.
Mountains being built from old seafloors. Volcanic islands rise in the middle of the ocean. Geysers of steam blast through vents from deep underground. Huge cracks in Earth’s crust with slowly moving plates of rock move in different directions on either side. Even entire continents move slowly around Earth’s surface as though they float on the surface of a liquid globe. WOW! Lots of action – but very slow motion!
Most of Earth’s insides are hidden from us. Many of these events have been difficult to understand. As geologists and their equipment become more advanced, sophisticated measurements can be used to support the concepts we use to explain what is happening.
Figure E.S.3.3 – Notice the lines on Mt. Robson.
Those are layers of sedimentary rock.
Figure E.S.3.4 – Earthquakes and volcanoes are found near plate boundaries.
Words to Think About:
Check out the word cloud below. It pictures the important words that you are going to learn in this section. Watch for these words, and combinations of these words, as you read. When you see them highlighted, you can click on them to learn more about
what the word means.
You can also visit the course glossary and read definitions for all of these words.
Lessons in This Section
Lesson E10: Continental Drift
Key Question – What evidence suggests that Earth’s continents move and were all attached as a supercontinent at some time in the past?
Lesson E11: Plate Tectonics
Key Question – What is a tectonic plate, and what happens in the regions where tectonic plates meet?
Lesson E12: What is a Hotspot?
Key Question – What is a hotspot, and how does it reveal the speed of a tectonic plate?
Lesson E13: The Majestic Rocky Mountains
Key Question – How did the Rocky Mountains form?
Reading and Materials for This Section
Science in Action 7
Reading: Pages 392–408
Materials Lists for Unit:
Think • Interpret • Decide
Figure E.S.3.5 – What could cause sedimentary rock, originally deposited as horizontal layers, to become a folded mountain as in this example?
Figure E.S.3.6 – Most of the Rocky Mountains are folded and faulted sedimentary rock that was deposited at the bottom of shallow seas.. Photo by
Jeff Hitchock
Look closely at the two photos above (Figures E.S.3.5 and E.S.3.6). Mt. Kidd is located just west of Calgary. You might be able to visit Mt. Kidd on a beautiful summer day, but you can visit it virtually by
clicking here.
How did the unique wavy lines form in these majestic mountains? Look at this video showing a pile of towels being pushed together from both ends:
How did the unique wavy lines form in these majestic mountains? Look at this video showing a pile of towels being pushed together from both ends:
Questions:
Think about the following questions very carefully. Then, type or write your answers. When you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. When you have your answers, click the questions for feedback.
The rock process illustrated by the towel example is called folding.
Solid rocks can bend over long periods, especially when large amounts of pressure are applied to them.
These forces are found where large pieces of rock, which are slowly moving along Earth’s surface, crash into each other in slow motion. Rocks can also ‘fault’ when put under pressure. If a fold is the same as a bend, can you guess what a fault is? A fault
is when rock breaks
Does it seem possible that something as solid as rock can change like this? This is just one example of the amazing changes to Earth’s surface that you can see around you. You will be learning much more about changes to Earth’s surface in this section.