1. Geology
Chapter 15

2. Geology
The science devoted to the study of dynamic processes occurring on the Earth’s surface and in its interior

3. Essential Question #1
What are the characteristics of the three major concentric zones of earth?

4. Three Concentric Zones
Core – innermost zone
Extremely hot
Solid inner part surrounded by liquid molten material
Mantle – middle zone
Outermost part is solid rock
Asthenosphere = inner part made of hot partly melted pliable rock that flows
Crust – outermost zone
Continental crust
Oceanic crust

5. Earth’s Crust and Upper Mantle
Our knowledge of the earth’s interior comes mostly from indirect evidence such as density measurements, seismic (earthquake) wave studies, measurements of interior heat flow, lava analysis, and research on meteorite composition.
Lithosphere = Crust and outermost Mantle

6. Tectonic plate Mantle Hot outer core Inner core Spreading center
Collision between two continents
Oceanic tectonic plate
Oceanic tectonic plate
Ocean trench
Plate movement
Plate movement
Tectonic plate
Oceanic crust
Oceanic crust
Subduction
zone
Continental crust
Continental crust
Cold dense material falls back through mantle
Material cools as it reaches the outer mantle
Hot material rising through the mantle
Mantle convection cell
The earth’s crust is made up of a mosaic of huge rigid plates, called tectonic plates, which move around in response to forces in the mantle.
Mantle
Two plates move towards each other. One is subducted back into the mantle on a falling convection current.
Hot outer core
Inner core
Fig. 15-3, p. 337

7. Essential Question #2
How does the movement of tectonic plates shape the earth’s surface and other zones?
Internal Processes = driven by heat from the earths interior

8. Tectonic Plates
Convection cells (currents) in the mantle move large volumes of heat and rocks in loops, causing the movement of large rigid plates (lithosphere) on the earth’s surface.
Tectonic plates composed of lithosphere, continental crust / oceanic crust + outermost part of mantle.
Move at about the rate that fingernails grow; imperceptible.

9. Tectonic Plate Boundaries
The extremely slow movement of the tectonic plates causes them to grind into one another.
Convergent – push two plates together
Divergent – spread plates apart (oceanic)
Transform – plates slide past each other

10. Tectonic Plate Boundaries
Convergent Plate Boundaries
Subduction - Continental plate usually pushes oceanic plate down into mantle
Forms a trench in ocean & mountains on land
Divergent Plate Boundaries
As oceanic plates spread apart, molten rock (magma) pushes up the cracks forming ocean ridges
Transform Faults
Plates slide and grind past one another along a fracture (fault) in the lithosphere
Mostly in oceans
San Andreas Fault , CA

12. Major Tectonic Plates & Boundaries

13. Volcanos
Often form along the boundaries of tectonic plates where magma can escape in the form of lava
Volcanic eruptions releases lava rock, hot ash, liquid lava, and gases such as water vapor, carbon dioxide and sulfur dioxide.
Large eruptions can alter climate for extended periods of time (cooling effect).
Benefits include land formation and increased soil fertility.

14. Ring of Fire Huge ring of volcanic and seismic activity
Includes 452 volcanos; over 75% of world’s active and dormant volcanos
About 90% of the world’s earthquakes & 81% of the world’s largest earthquakes occur here
Around the Ring of Fire, the Pacific Plate is colliding with and sliding underneath other plates. This process is known as subduction and the volcanically and seismically active area nearby is known as a subduction zone. There is a tremendous amount of energy created by these plates and they easily melt rock into magma, which rises to the surface as lava and forms volcanoes.

15. Earthquakes Colliding plates create tremendous pressures in the crust
Earthquakes occur when stresses cause rocks to suddenly shift and break, forming faults
Abrupt movement of faults release stored energy in the form of seismic waves, which move in all directions through the surrounding rock
Focus = place where an
earthquake begins
Epicenter = place on the surface
directly above the focus
Severity measured in magnitude of seismic waves causing the ground to move (shake).
Measure using instrument called seismograph.

16. Earthquake in Haiti – January 2010
7.0 Magnitude, followed by at least 52 aftershocks 4.5 or greater
Over 220,000 dead; damaged 250,000 residences & 30,000 commercial buildings
Despite humanitarian aid efforts, over 370,000 people still without homes today

17. Ocean Earthquakes & Tsunami’s
Tsunami = a series of large waves generated when part of the ocean floor suddenly rises or drops

18. Indian Ocean Tsunami
9.15 Magnitude earthquake on ocean floor generated waves as high as 100ft
Killed ~228,000 people in Indonesia, Thailand, Sri Lanka, South India & Eastern Africa
Photos show Banda Aceh Shore near Gleebruk in Indonesia

19. Japan Tsunami
9.03 magnitude earthquake on ocean floor generated waves as high as 133ft
Over ~16,000 reported dead/missing
Estimated economic cost $235 billion (US) – costliest natural disaster in world history
Meltdown of Fukushima Nuclear Power Plant as a result of the Tsunami became the worst nuclear disaster in world history (level 7 meltdown). Worse than Chernobyl.

20. How do physical, chemical and biological weathering generate soil?
Essential Question #3
How do physical, chemical and biological weathering generate soil?
External Processes = based directly or indirectly on energy from the sun or gravity

21. Weathering
The physical, chemical, and biological processes that break down rocks and minerals into smaller particles that help build soil.

22. Weathering Physical (Mechanical) Weathering Chemical Weathering
Large rock broken down into smaller pieces
Chemical Weathering
One or more chemical reactions slowly dissolve the minerals in rocks
Biological Weathering
Conversion of rocks or minerals into smaller particles through the actions of living things

23. Parent material (rock)
Biological weathering
(tree roots and lichens)
Chemical weathering
(water, acids, and gases)
Physical weathering
(wind, rain, thermal expansion and contraction, water freezing)
Physical, chemical, and biological processes can weather or convert rock into smaller fragments and particles. It is the first step in soil formation.
Particles of parent material
Fig. 15-6, p. 340

24. Erosion
The process by which material is dissolved, loosened, or worn away from one part of the earth’s surface and deposited elsewhere
Mostly caused by flowing water, rain, wind, and human activities that destroy vegetation that holds soil. Glaciers can also cause erosion.

25. Mass Wasting
When rock and soil become detached from underlying material and move downhill under the influence of gravity
Rockslides, landslides, and mudslides.

26. Essential Question #4
What are the three classes of rocks, and how are they recycled by the rock cycle?

27. Rock
A solid combination of one or more minerals that is part of the earth’s crust

28. 3 Types of Rock Igneous Sedimentary Metamorphic
Forms when molten rock (magma) wells up from the earth’s upper mantle, cools, and hardens
Sedimentary
Forms from sediment produced when existing rocks are weathered and eroded into small pieces
Compaction (pressure) + Cementation (minerals seeping through sediment deposits) bind particles forming rock
Metamorphic
Forms when a preexisting rock is subjected to high temperatures / pressures, chemically active fluids, or a combination
Igneous forms the bulk of earth’s crust, although it’s often covered by sedimentary rock or soil. Main source of many metal and nonmetal mineral resources.

29. Erosion Transportation Weathering Deposition Igneous Rock
Granite, pumice, basalt, lava rock
Sedimentary Rock
Sandstone, limestone, shale, dolomite, bituminous coal
Heat, pressure
Cooling
Heat, pressure, stress
Magma (molten rock)
The rock cycle is the slowest of the earth’s cyclic processes. The earth’s materials are recycled over millions of years by three processes: melting, erosion, and metamorphism, which produce igneous, sedimentary, and metamorphic rocks. Rock from any of these classes can be converted to rock of either of the other two classes, or can be recycled within its own class.
Melting
Metamorphic Rock
Slate, marble, gneiss, quartzite
Fig. 15-8, p. 343

30. Soil: A Renewable Resource
Chapter 3

31. What is soil and why is it important?
Essential Question #5
What is soil and why is it important?

32. Soil
A thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, and billions of living organisms (most of them microscopic decomposers) Soil is a renewable resource that is renewed very slowly (100’s to 1000’s of years)

33. Ecological Services of Soil
Supply nutrients to producers
Cleanses & stores water
Important in biogeochemical cycling
Decomposes organic matter
Helps control climate by sequestering carbon
Habitat for soil organisms
Scientific research - antibiotics

34. Economic Services of Soil
Supports agriculture industry
Food, feed, fiber, fuel, etc
Provides food security
Stores solid waste
Foundation for cities and towns

35. Soil & Human Civilization
Human activities have accelerated natural soil erosion since the beginning of agriculture
Mismanagement turns soil into a
nonrenewable resource
Sophisticated civilizations such as the Mayans, Easter Island, Harappan (India) ended as a direct result of mismanaging soil
The Norse people who settled Greenland survived for 450 years before destroying the vegetation and soil that supported them.
Sumerian civilization (4th century BC) collapsed mostly because long-term irrigation led to salt buildup in its soils and declining food productivity.
Early settlers ecologically devastated Iceland, but the people learned from their mistakes & now have one of the world’s most environmentally sustainable countries and a prosperous economy.

36. Essential Question #6
What are the three sizes of particles that compose soils, and how do they determine soil texture?

37. Soil Particle Size
Sand
Largest
Silt
Medium
Clay
Smallest

38. Physical Properties of Soils
Soil Texture
Relative proportions of sand, silt & clay particles in a soil
Measured using Soil Triangle
LOAM Soil = BEST for plant growth
Permeability
The rate at which water moves through soil
Porosity – the amount, size and arrangement of pores between particles
Water Holding Capacity
Ability of pores to hold water for plant use
Soil Compaction - destoys the quality of the soil because it restricts rooting depth and decreases pore size. The effects are more water-filled pores less able to absorb water, increasing runoff and erosion, and lower soil temperatures.

39. Soil Texture Triangle

40. Chemical Properties of Soil
Soil Salinity and Interpretation
Chemical Properties of Soil
Conductivity (mmho/cm)
Interpretation
4 or above
Severe accumulation of salts. May restrict growth of many vegetables and ornamentals.
2 to 4
Moderatre accumulation of salts. Will not restrict plant growth, but may require more frequent irrigation.
less than 2
Low salt accumulation. Will not affect plants.
Nutrients
Primary: Nitrogen (N), Phosphorus (P), Potassium (K)
Secondary: Sulfur (S), Calcium (Ca), Magnesium (Mg) pH
Affects availability of plant nutrients
Optimal pH between 5.5 – 7.5
More acidic soils hold more toxic nutrients
Affects soil organisms & nutrient cycling
Salinity
Salts come from irrigation water, fertilizers, composts & manure
Dolomite lime, calcium carbonate, and wood ash can increase soil pH.

41. Microorganisms are the driving force for nutrient release to plants
Organic Matter & Soil
Microorganisms are the driving force for nutrient release to plants