1. 1.4: Land Form Patterns: Plate Tectonics & Lab
World Geo 3202
Unit 1: Land Forms Water Forms
September 2011

2. Outcomes In this lesson you will:
1.1.1 Explain how compressional forces are caused. (k)
1.1.2 Explain how tensional forces are caused. (k)
1.1.3 Relate selected plate movements to compressional and tensional forces. (a)

3. Earth
To begin this unit we will look at the external and internal sections of the earth
The exterior consists of land & oceans
Topography: is a general term referring to the surface features of the earth like, hills, mountains, valleys, plains, plateaus and other relief features.
Complete the map activity before we explore the interior

4. Topography Review
Imagine you flew from the west coast of South America to the east coast and you flew right along the equator. What land forms would you fly over?

6. Earth’s Interior
The earth's interior is neither all solid nor is it all molten.
There are layers with a different density, thickness and composition.
Furthermore the earth's crust is not one continuous layer.
It is broken into many sections known as plates. Some plates are quite small while others are quite large.

7. Earth’s Interior
They all float and move on top of the molten asthenosphere.
When these plates push together and when they pull apart they create "tectonic forces".
It is interesting to note; without this liquid layer called the asthenosphere we would not experience earthquakes or volcanoes.
The Earth’s Interior (Worksheet 1.1)

8. Plate Tectonics

9. Plate Tectonics

10. Patterns of Plate Movement
When any objects move separately, we either get movement towards each other or movement away from each other
Regarding plate tectonics, we call this movement towards or away as compressional or tensional

11. Compressional Forces occur where two tectonic plates come together, they compress & squeeze against each other causing rock layers to bend, warp, or be pushed upwards .
Subduction Zones sometimes occur where compressional forces result from two plates colliding.

12. Compressional Forces and Subduction Zones
Plate Tectonics

13. Compressional Forces and Subduction Zones
Plate Tectonics

14. Tensional Forces occur where two tectonic plates are pushed apart (stretched). The tension is created as the plates move away from each other which sometimes forms a trench as one plate drops downward.
Ridge Zones sometimes occur where two plates move apart. The magma rises between the plates and forms a ridge.

15. Tensional Forces and Ridge Zones
Plate Tectonics

16. Tensional Forces and Ridge Zones
Plate Tectonics

17. Plate Tectonics Lab

18. Major Mountain ranges tend to coincide with subduction zones at the boundaries between two converging plates.
The tremendous compressional forces literally fold the thin crust in to mountains over millions of years.

19. Volcanoes can occur at subduction zones or at ridge zones.
At subduction zones the compressional forces sometimes leave a crack in the crust that allows the magma to reach the surface.
At ridge zones the plates are moving apart which allows magma to reach the surface from the asthenosphere.
Because of the excessive number of active volcanoes on the coast around the pacific ocean it is known as the Pacific Ring of Fire.

21. Earthquakes often occur at transform zones where the plates are moving beside each other instead of toward or away from each other.
Look Closely at figure 1.10 on page 12 and you can see transform zones where the plates are moving side by side.

23. Notice that subduction zones occur where the tectonic plates are moving towards each other while Ridge zones occur where the plates are moving apart and transform zones occur where plates are moving side by side.
Notice that the Americas (North American Plate and South American Plate) are moving away from Europe and Africa (Eurasian Plate and African Plate.

24. Plate Tectonics Lab