1. Chapter 5: Earth’s Changing Surface
Ms. Johnson
Foundations

2. Objectives
Earth’s surface undergoes constant changes as a result of internal and external forces. Minerals are characterized by certain physical and chemical properties. Rocks, which make up Earth’s crust, can be either igneous, metamorphic, or sedimentary. The three types of rocks are subject to processes that can change any one type into any other type; these processes make up the rock cycle. External forces that change Earth’s surface include weathering and erosion. Internal forces that shape the Earth’s surface produce mountains, earthquakes, and volcanoes.

3. Vocabulary Surface Materials Internal Forces Minerals Plate tectonics
Crust
Bedrock
Soil
Minerals
Physical properties
Hardness
Cleavage
Color
Chemical properties
Rocks
Igneous rocks
Sedimentary rocks
Metamorphic rocks
External Forces
Weathering (physical & chemical)
Erosion
Gravity, water, glaciers, wind
Internal Forces
Mountains
Folding
Faulting
Earthquakes
Volcano
Plains
Plateaus
Plate tectonics
Plates
Mantle
Continental drift
Ocean-Floor Features
Mid-ocean ridge
Trenches
Continental shelves
Continental slopes

4. Surface changes, surface materials, minerals, rocks, and the rock cycle.
Earth’s surface

5. Surface Changes
The surface of the Earth is constantly undergoing change.
New mountains rising
Rivers carve valleys
Large rocks get broken down
Two types of forces occur:
External forces and internal forces

6. Surface Materials The outer layer is called the crust.
Crust is made of bedrock, rock fragments, and soil.
Bedrock: the solid rock portion of the crust
At the surface it is called outcrop
Can range from giant boulders to sand
Soil: mixture of small rock fragments and organic matter.
Soil and rock fragments make up most of the surface with bedrock underneath.

7. Minerals Rocks are composed of minerals
Quartz
Rocks are composed of minerals
Minerals: naturally occurring solid substances made of inorganic (nonliving) material.
Ex. feldspar, quartz, mica, and calcite
Mica
Calcite

8. Minerals Physical Properties
Hardness: the resistance of a mineral to being scratched.
Scale of 1-10, 1 is soft, 10 is hard
A mineral can be scratched by another mineral if it is higher on the hardness scale
Cleavage: a mineral’s tendency to break along smooth, flat surfaces.
Not all minerals have cleavage, some break unevenly
Color: literally the color.
Not always reliable because some minerals can be the same color
Color is helpful when combined with other properties
Chemical Properties
How minerals react with chemicals
Ex. Calcite fizzes when HCl is placed on it

9. Rocks
Rocks: natural, stony materials composed of one or minerals that form the Earth’s crust.
Can be identified by physical and chemical properties
Three groups:
Igneous
Metamorphic
Sedimentary

10. Igneous Rocks
Produced by the cooling and hardening of hot, liquid rock (magma-underground, lava-above ground). Identified by their color and the size of the crystals they contain.
Igneous rocks that form from the rapid cooling of lava contain tiny crystals
Basalt- a dark colored volcanic rock composed of micro crystals (too small to be seen)
Igneous rocks that form underground by slow cooling magma develop large crystals
Granite- a light-colored rock that contains easily visible mineral grains

11. Igneous Rocks
Grain size of igneous rocks depends on the rate and depth at which magma cools
The closer to the surface, the smaller the grain size (crystals) in the rock.

12. Sedimentary Rocks
Form from particles (sediments) that pile up in layers.
Sediments: small rock fragments or seashells
They usually form underwater.
They form when sediments are carried down moving water and eventually settle to the bottom
The longer they are at the bottom, they start to harden into rock material
As the water carries sediments, it drops the largest sediments first, then the smaller ones.

13. Sedimentary Rocks
After sediments accumulate for millions of years, they become buried deep in the earth and harden into sedimentary rocks.

14. Metamorphic Rocks
Produced when igneous and sedimentary rocks undergo a change in form caused by heat, pressure, or both.
This can happen when magma comes in contact with rocks
Underground forces squeeze rocks for a long time
The appearance and mineral composition gets altered

15. Metamorphic Rocks Metamorphic rocks: Marble and slate
Marble forms from limestone (sedimentary)
Slate forms from shale (sedimentary)
Metamorphic rock: Gneiss
Produced from granite (igneous)

16. The Rock Cycle
Rocks can change from one type to another by the processes shown.

17. Forces that change Earth’s surface
External forces, internal forces, plate tectonics, and ocean floor features.
Forces that change Earth’s surface

18. External Forces
Various forces are always at work shaping and changing Earth’s surface. External forces: include the processes of weathering and erosion.

19. External Forces: Weathering
Weathering: the breaking down of rocks into smaller pieces.
Physical weathering: rock is broken into smaller fragments by physical agents
Ex. the roots of plants growing in cracks force rocks to break apart
Chemical weathering: the breaking down of rocks through changes in their chemical makeup
Takes place when rocks are exposed to air or water
Ex. acid rain dissolves certain minerals in rocks and causes them to fall apart
By breaking down rocks into smaller fragments, the processes of weathering assist in the formation of soil.

20. External Forces: Erosion
Erosion: the process by which rock material at Earth’s surface is removed and carried away.
Requires a moving force such as flowing water
Gravity and water play important roles in erosion.
Gravity is the force that moves water and rock downhill
Ex. The Grand Canyon was formed by erosion caused by running water.

21. External Forces: Erosion
Groundwater and glaciers also cause erosion.
Groundwater: forms from rain or snowmelt that filters into soil, it seeps into bedrock and carries material away
Ex. formation of underground caves
Glaciers: masses of ice that form in places where more snow falls in winter than melts in summer
Gravity carries the ice downhill and as it moves it grinds up and removes rock material
Wind
Wind can carry sediments which scrape along outcrops and slowly carve them away
The forces of erosion are always at work, moving rock material from land into the ocean basins.

22. Internal Forces
Internal forces include: mountains, earthquakes, and volcanoes They raise the land and build up Earth’s surface

23. Internal Forces: Mountains
Mountains: produced mainly by the processes of folding and faulting
Folding: forces in the crust push rocks together bending the layers into folds forming ridges and valleys
Faulting: forces in the crust squeeze or pull rock beyond its stretch max. (there are many different types of faults)

24. Internal Forces: Earthquakes
Earthquakes: sudden movements of rocks sliding along faults that produce strong vibrations- cause land uplift and mountains

25. Internal Forces: Volcanoes
Volcano: a hole in Earth’s crust through which lava flows from underground.
The lava cools and forms solid rock, building upward in layers

26. Internal Forces: Plains & Plateaus
Plains: broad, flat regions found at low elevations
Made of layered sedimentary rocks
Plateaus: large areas of horizontally layered rocks with higher elevations than plains

27. Plate Tectonics
Plate tectonics: the forces and movement at work inside the Earth that raise the level of the land.
The earth is broken up into a number of large pieces (plates) that move and interact.
Plates can move apart, slide past each other, or collide.
Spread apart: ocean basins form
Slide past each other: earthquakes occur
Collide: mountains form
It is believed that plate motions are caused by heat circulating in Earth’s mantle (beneath the crust)

28. Ocean Floor Features
75% of the Earth’s surface is covered by ocean water and underneath it, it is not flat and featureless. Mid-ocean ridge: a long, underwater mountain chain where rising magma forms new ocean crust. Trenches: underwater valleys that form the deepest part of the ocean floor.
Continental shelves: areas of the seafloor that gently slope away from the coastlines of most continents; the angle is very slight, if you stood on one you would think you were on level ground. Continental slope: a steep drop from the outer edge of a continental shelf to the great depths of the ocean.

29. Ocean Floor Features

30. Chapter 5: Earth’s Changing Surface
Questions?