PHYSICAL GEOGRAPHY, EXAM 3 (CH 12-14) STUDY GUIDE

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1 PHYSICAL GEOGRAPHY, EXAM 3 (CH 12-14) STUDY GUIDE NOTE: This guide is to cover some of the main topics we have discussed but does not cover everything on the exam. To do well, you need to carefully read and study the assigned chapters in the book. You may want to also look at other information online if that helps you. One good resource is: THE BIG PICTURE So far we have been talking about different spheres or kinds of big systems that operate on a global scale. These spheres are ideas that we have that let us think about different parts of the systems of the earth that go together. Right now we are studying the Lithosphere System, but it is important that we don t just think of it as tectonic plates, and rocks, but that we understand how it fits with the big picture of this class. 1. Think of the whole earth as one big system it does many things, gets energy from the sun (and a little from within the earth) and it sends it back as heat energy. To make things easier, we break this big system into some related sub-systems: a. The Atmosphere System This includes sun-earth relationships, weather and climate, etc, basically actions that involve the atmosphere, or gasses above the Earth s surface. b. The Lithosphere System This involves the processes that take place in the solid part of the Earth below the Atmosphere. This is what we are focusing on for this exam and we will go into detail below this. The study of the lithosphere in geography is called geomorphology. c. The Hydrosphere System This includes any process that involves water. Hydrosphere Systems will overlap with actions in the Atmosphere and Lithosphere (and Biosphere too!) because water exists and acts both in air and on land, and also interacts with living plants and animals. After this exam, we will be talking about the Hydrosphere. d. The Biosphere System This includes any process that involves living things like (plants and animals) and organic matter which comes from living things and is part of the soil. The Biosphere will overlap with all other spheres. The interaction of living things (the Biosphere) with the nonliving (also called abiotic) parts of the Earth (Atmosphere, Lithosphere, Hydrosphere) is what we call ecology. The Lithosphere System While nothing may seem more stable or unchanging as mountains and continents, one thing we are learning is that these indeed change over time, but over a very LONG period of time. In the Lithospheric System, there are different sets of processes that build things up and that wear things down. We call these endogenic and exogenic processes. Endogenic These are internal processes remember that the other word exogenic is like external to help you remember that endogenic is like internal. These are processes that use energy stored inside the earth (internal energy) and they are responsible for building up landscapes (mountains, islands, continents, etc ) Exogenic These are external processes. Generally speaking, these are forces that wear things the things that were built up by endogenic processes. They tend to flatten the landscape as they break up and wear down built-up mountains or other landscape features. Endogenic processes can act on the force of gravity alone or with the help of other geomorphologic agents such as running water, moving ice, or the wind. For this exam we are focusing on exogenic processes powered by gravity such as mass wasting. We will cover other forms of exogenic processes that involve water, ice, and wind for the next exam. 1

2 CHAPTER 12. EARTH S INTERNAL SRUCTURE, ROCK CYCLE, GEOLOGIC TIME Earth s planetary structure Know what the Asthenosphere is and why it is important. Remember that it is the fluid, or movable layer beneath the ridged layer we call the Lithosphere. Read about it and be prepared to locate the layers shown in Figure 10.3 (Asthenosphere, Lithosphere, Oceanic crust, Continental crust). Earth s crust Understand the differences between oceanic and continental crust. Understand that oceanic crust is made up of basaltic rock that is denser than the granitic rock that makes up continental crust. Why is that important? Be prepared to explain why this is important and me if you do not understand why. The rock cycle Be prepared to draw a diagram of (like Figure 10.18) and explain the rock cycle and in particular: How do igneous rocks form? What happens to them after they are above ground and exposed to weather and gravity for a long time? What happens to the material that breaks away from igneous rocks, or where does that end up? Be prepared to explain how sedimentary rocks form. What happens to sedimentary rocks once they end up on the edge of an oceanic plate that converges with a continental plate, or how can sedimentary rocks become metamorphic rocks and later become magma that could form new igneous rocks? Generally speaking, what kind of rocks are the Sierra Nevada, and what kind are the California Coast Ranges? Plate tectonics Plate tectonic movement Be prepared to explain plate tectonics and in particular: Plate divergence, or Seafloor spreading how does that work and how does it affect the movement of oceanic plates? Plate convergence and Subduction When oceanic plates move away from a spreading center (see sea-floor spreading), what happens at the other end of the plate that comes in contact with a continental plate? (Hint: here it is important to know which denser: oceanic or continental crust). Transform movement of plates what kind of movement is this? Be prepared to answer or explain what kind of plate boundary is at the San Andreas Fault. 2

3 Hot Spots - What are hot spots? Be prepared to explain how the Hawaiian Islands were formed. Paleogeography is the study of the past geographical environments. You don t need to memorize all of the epochs, periods, eras, and eons, but I d like you to know: 1. These time periods are not at fixed intervals but separated by big events that have been discovered by looking at layers of rocks, fossils, etc a. Be prepared to put these terms in the correct order in terms of how big of a time period they are (from longest to shortest): Eon, Era, Period, and Epoch. We are currently in the Cenozoic Era, Quaternary Period, Holocene Epoch. b. What event separates the current era (Cenozoic) from the one before it (Mesozoic) and about how long ago was that? c. About how long have we been in the current Epoch (Holocene, ~15k years) and what event separates it from the previous Epoch (Pleistocene, ice ages) CHAPTER 13. TECTONIC PROCESSES AND LANDFORMS Landforms and Geomorphology Landforms types of surface features (mountains, canyons, valleys, etc ) Geomorphology Subfield of geography that studies landforms Topography distribution of landscape (mountains, plains, hills, valleys, plateaus) Relief Differences between highest and lowest elevation in an area Low relief areas are relatively flat High relief areas are mountainous or rugged Pluton a body of magma that cooled and formed rock under the Earth s surface (underground). Batholith The largest types of plutons are called a batholith, or a large area of igneous rock that cooled from magma underground. These form the large mountain ranges in western North America, particularly the Sierra Nevada next to us (that is why it has so much granite!). But if a batholith forms underground, why are the granitic mountains of the Sierra Nevada above ground? Be able to explain how a batholith below the surface becomes mountains above the surface. In short it is because the rock is harder than other types of rocks that cover it. As the softer rocks above it are worn or eroded away though exogenic processes, the harder does not wear away as fast so remains where other softer material has worn away. 3

4 Tectonic forces (Be prepared to identify and explain Figure 14.25) So we understand that tectonic forces move Earth s crust around and as it does this, parts of the Earth s crust is pushed against each other, pulled apart from each other, or slide past each other. These form distinct types of landforms depending on the type of force. Compressional tectonic forces push to areas of crustal rocks together Faulting Tends to shorten, or thicken the crust Will cause folding or faulting in the landscape One way rocks may react when pushed together is by breaking apart from each other, with one set of crustal rocks moving up and one moving down this is called a fault Folding Sometimes rocks don t break when pushed together but they fold. Remember the types of folds shown in Figure Anticline is a fold that is shaped like a dome and syncline is a fold that is shaped like the letter U. Tensional tectonic forces pull areas of crustal rocks apart Tends to stretch, or thin the crust Can cause the crust to be broken into fault blocks (Figure 14.29) o The fault blocks that are pushed up are called horsts o The fault blocks that slip down are called grabens o These form what is called a host and graben landscape Shearing tectonic forces areas of crustal rock slide past each other I won t require all the details but know that San Andreas Fault is due to shearing tectonic forces Earthquakes When force builds up in crustal rock and is released suddenly, this causes an earthquake Magnitude o Richter scale Numeric scale - each number is 10x movement, 30x energy o Modified Mercalli scale more about the effect of earthquake on people and structures Focus - Point in the earth where quake originated Epicenter - Surface location (directly) over the focus, Quake strongest here Ring of fire - Area around Pacific with greatest concentration of destructive quakes 4

5 CHAPTER 14. WEATHERING AND MASS MOVEMENT This chapter deals with exogenic processes Again, be able to explain the difference between endogenic an exogenic processes. Weathering Physical weathering Does not involve chemical reactions Unloading (p. 413) rocks are under pressure (from other rock on top of them) when they are underground. As softer material wears away and rock becomes exposed, it is under less pressure. This causes the outer layers of rock to break away. Freeze-thaw weathering In areas subject to freeze-thaw cycles, water gets into rock cracks, then it freezes and expands breaking rock apart. In what type of climate do you find this? Salt crystal growth similar to freeze-thaw but in this case water has salt crystals that grow when the water evaporates from the rock. In what type of climate do you find this? Hydration the addition of water causes minerals in the rock to expand Chemical weathering Involves chemical reactions I will not require you to remember details of specific types but understand that chemical weathering usually requires the presence of water and works faster when it is hot. This is important because it tells us something about the type of climate in which we might find chemical weathering (wet and hot). Variability in weathering Climate and Weathering (Figure 14.1) How does climate affect the type of weathering one might experience in an area? When we are talking about climate, let s think of it in terms of out two controls temperature and precipitation, or how hot/cold or how wet/dry a place is: Mass wasting Freeze-thaw weathering areas with cold winters (because the water has to freeze) Salt crystal growth areas that are hot/dry (because the water has to evaporate) Chemical weathering hot and wet climates (need water and heat for chemical reactions) Can be classified by types of earth material and speed of motion (see Table 12.1) Slow mast wasting o Creep o Solifluction Fast mass wasting o Falls o Avalanches o Slides o Flows 5