AP Environmental Science Unit 4 Review (Everything You Need to Know!)

Summary

In this engaging and comprehensive review of AP Environmental Science Unit 4, Mr. Smees guides students through a journey into Earth science. The video moves beyond the ecological concepts of Unit 3 to explore plate tectonics, soil formation, the atmosphere, watersheds, and oceanic phenomena like El Niño. With a focus on understanding complex systems and interconnections, students are encouraged to think critically about Earth's dynamic processes. Highlights include the role of plate tectonics in shaping landforms, the crucial composition of soil, and the impact of atmospheric layers and their characteristics. The video wraps up with insights into global wind patterns and the fascinating effects of El Niño and La Niña on our climate.

Highlights

• Plate tectonics play a significant role in shaping Earth’s landforms with convergent, divergent, and transform boundaries leading to various geological features! 🚀
• Soil is a dynamic and complex system composed of sand, silt, clay, and organic matter crucial for plant growth and environmental filtration! 🌱
• The atmosphere's layered complexity affects weather and climate, with the troposphere being the lively locale for weather phenomena! ☁️
• Learn about Hadley Cells and how global wind patterns and pressure systems shape climate zones and influence weather worldwide! 🌬️
• The fascinating El Niño and La Niña events dramatically alter weather conditions across the globe, affecting everything from rainfall to fisheries! 🎣

Key Takeaways

• Dive deep into Earth's structure with Unit 4's focus on plate tectonics, the mysterious mantle, and how they shape our world! 🌍
• Uncover the secrets of soil and why it’s way more than just 'dirt'—it's a life-brimming mixture that sustains us! 🍂
• Navigate the layers of the atmosphere and understand their roles in protecting and regulating life on Earth! 🌌
• Explore the importance of watersheds and how they influence water quality and availability in ecosystems! 💧
• Understand the dynamic dance of El Niño and La Niña and their impact on global climate patterns! 🌊

Overview

Welcome to an exciting venture into APES Unit 4, where we move beyond the lush landscapes of biodiversity into the grand geological forces that mold our planet. Mr. Smees kicks things off with the riveting details of plate tectonics, illustrating how these gigantic slabs carve landforms through their monumental movements and collisions. It's a literal journey to the center of the Earth as we dive into the mantle's molten mysteries and the earth-shaping power of tectonic boundaries! 🔥

Next up, prepare to have your preconceptions about soil turned upside down! Mr. Smees unravels the complex tapestry of what we casually call 'dirt', revealing its crucial role as a thriving ecosystem that filters, nourishes, and supports all terrestrial life. By understanding the intricate balance of components from clay and silt to organic matter, students come to appreciate why soil is fundamental to our environmental existence. 🌱

Finally, ascend into the atmospheric wonders and oceanic oscillations that govern our climate. The session climaxes with a deep dive into the atmospheric layers and the sweeping influence of the El Niño Southern Oscillation. Grasping these concepts is essential, as they explain significant global weather patterns and their impact on biodiversity and human activity alike. 🌎

Chapters

• 00:00 - 01:00: Introduction and Overview The chapter begins with Mr. Smees welcoming students to Unit 4 of the AP Environmental Science ultimate review packet. He emphasizes the importance of having the review packet printed out for better understanding and revisiting topics. Mr. Smees offers timestamps for easy navigation to specific topics within Unit 4. The focus of Unit 4 shifts from ecology, biodiversity, and populations covered in Unit 3, to a deep dive into earth science, signaling a metaphorical and literal descent into the subject.
• 01:00 - 03:00: Plate Tectonics and Boundaries In this chapter, we delve into the mechanics of the Earth's structure, starting with plate tectonics. We'll explore the dynamic boundaries of these massive lithospheric plates and how they influence the formation of Earth's landforms. The chapter emphasizes understanding tectonic plates as massive rock slabs floating on the molten mantle, highlighting the interaction between tectonic shifts and geological formations.
• 03:00 - 07:00: Soil Composition and Formation The chapter 'Soil Composition and Formation' delves into the physical and chemical dynamics beneath the Earth's surface that influence soil formation. It begins by explaining how the Earth's core, composed of nickel, iron, and radioactive elements, releases heat through decay, affecting tectonic activity. This heat plays a crucial role in the movement of tectonic plates, which float on the Earth's mantle. The movement and interactions of these plates, specifically at divergent boundaries where they move apart due to rising magma, are significant in shaping the Earth's landforms. The chapter underscores the importance of geological activity in the formation and alteration of soil structures over time.
• 07:00 - 10:00: Soil Properties and Fertility The chapter discusses geological processes involving tectonic plates, specifically focusing on the concepts of seafloor spreading and plate boundaries.
• 10:00 - 15:00: Atmosphere Composition and Layers The chapter explains the different types of plate boundaries and their characteristics. It specifically discusses convergent plate boundaries, where one plate slides beneath another, and how these can form volcanic mountain ranges and trenches. It also covers transform plate boundaries, sometimes referred to as transform faults, where two plates slide past each other in opposite directions, leading to earthquakes as a result of stuck or locked plates despite the underlying force of magma.
• 15:00 - 18:00: Global Wind Patterns and Hadley Cells The chapter begins by explaining how tectonic plates interact with one another and how this interaction can lead to earthquakes. It describes how the plates are locked in place by friction until the force of underlying magma causes them to slide all at once, releasing energy in the form of earthquakes. The chapter then transitions into a new topic, covering soil science and clarifying the difference between soil and dirt, setting the stage for a detailed exploration of this essential part of the ecosystem.
• 18:00 - 21:00: Watersheds and Water Movement The chapter titled 'Watersheds and Water Movement' begins by highlighting the complexity of soil, often mischaracterized as just dirt. It describes soil as a mix of weathered rock particles like sand, silt, and clay, along with organic matter, both living, like microbes, and non-living, like decomposing leaves and animal waste. Additionally, it emphasizes the significance of pore space in soil, which is essential for oxygen and water to infiltrate, thereby providing roots with necessary access to these elements for plant growth. The chapter sets the stage to further explore how soil forms.
• 21:00 - 26:00: Earth's Seasons and Insolation The chapter discusses the inorganic or mineral components of soil, emphasizing their origin from the weathering of rocks. The process involves rain and the freeze-thaw cycle breaking down rocks into smaller pieces, referred to as the 'parent material.' The text humorously suggests the reason not to call soil 'dirt,' since it has 'parents.' Additionally, it highlights that soil comprises more than just rock fragments; it includes various horizons, with the topmost layer being organic matter.
• 26:00 - 31:00: Geography's Impact on Climate The chapter titled 'Geography's Impact on Climate' covers the different layers of soil and their characteristics. The O Horizon is the top layer filled with organic materials such as decomposers, plant roots, and partially decomposed matter like dead leaves. Beneath it is the A Horizon or topsoil, a crucial layer containing both organic matter and mineral components necessary for plant growth, such as nutrients like nitrogen and phosphorus, along with water and oxygen in its pore spaces. Following this layer is the B Horizon, or subsoil, which contains very little organic material.
• 31:00 - 39:00: El Niño Southern Oscillation (ENSO) This chapter explains the layers of soil, particularly focusing on the 'sea horizon' which contains parent material rocks that have undergone minimal weathering due to their depth. The distinction between weathering and erosion is also addressed; weathering refers to the breakdown of rocks, whereas erosion involves the movement of these rock pieces by natural forces like wind and rain. Erosion, while a natural process, can be exacerbated by human activity, leading to soil degradation.
• 39:00 - 42:00: Conclusion Soil erosion removes essential nutrients and microorganisms needed for plant growth and disrupts groundwater filtration. When rainwater infiltrates soil, pollutants are trapped within its layers, which helps in cleaning water before it reaches and recharges aquifers.

AP Environmental Science Unit 4 Review (Everything You Need to Know!) Transcription

• 00:00 - 00:30 hey everybody it's Mr smees and welcome to unit 4 of the Apes ultimate review packet make sure to have that packet printed out so you can follow along and make sure you're reviewing everything we go over in this video if you need to jump to a specific topic anywhere within unit 4 we have the time stamps right here so you can find exactly what you need if you're ready to think like a mountain and write like a scholar let's get started now unit 4 marks our descent literally and figuratively into the depths of earth science so we'll leave behind all the ecology biodiversity and population stuff we learned in unit 3
• 00:30 - 01:00 take a little deeper look at how the earth works we'll slide our way into plate tectonics infiltrate our way into watersheds unearth soil formation and all of its Mysteries we'll make sure to leave no stone unturned or unweathered okay sorry sorry I got on a roll on a topic 4.1 so the first thing we need to review in unit 4 is plate tectonics and how their boundaries help shape Earth's land forms now remember that tectonic plates are basically huge slabs of rock or lithosphere now these huge slabs of rock are floating on top of a molten magma sea that we call the mantle now the reason that that the mantle is a
• 01:00 - 01:30 liquid and not a solid is because of the heat given off by the Earth's core the earth's core is a dense ball of nickel iron and radioactive elements that decay and give off a tremendous amount of heat now that we know why tectonic plates are able to float on top of the mantle let's review how their movement and their collisions or the boundaries that they form ultimately shape all of the landforms we have on Earth the first type of plate boundary we'll review is a divergent boundary and that's where plates are moving away from each other due to a particularly hot portion of the mantle where Magma's Rising towards the surface and pushing them apart because
• 01:30 - 02:00 this typically happens between two oceanic plates we call it seafloor spreading this is how we get mid Oceanic features like trenches and underwater ridges now if we look at the plate on the right of this divergent boundary we can see that the magma at the divergent boundary is going to force it towards this continental plate this causes a convergent plate boundary where two plates are colliding now because it's more dense the oceanic plate is going to be subducted or forced beneath the continental plate now the subduction of this oceanic plate is going to force magma up through the lithosphere on the continental plate this is going to lead to volcanic mountain ranges forming
• 02:00 - 02:30 along the coast of this boundary in addition to volcanic mountain ranges these convergent plate boundaries can also form trenches right at the point where one plate is sliding beneath the other and finally we have transform plate boundaries sometimes called transform faults where two plates are sliding past each other in opposite directions now these transform plate boundaries are where we're most likely to see earthquakes occur that's because the two plates are trying to move past each other in opposite directions but they get stuck or they get locked so even though the force of the magma beneath them is still pulling them in opposite directions they're not moving
• 02:30 - 03:00 because they're locked with one another eventually when the force of the magma beneath them pulling them to opposite directions overcomes the friction between them at this locked fall they slide all at once releasing tons and tons of energy through the Earth's surface and that's what we call an earthquake now on topic 4.2 and 4.3 we'll take a look at the most misunderstood and the most underappreciated Topic in all of apes and that's soil not dirt and if you don't know the difference well you're about to find out so let's start with understanding what soil exactly is so we
• 03:00 - 03:30 can see why it's such a disservice to call it dirt soil is a complex mixture of tiny particles of weathered rocks such as sand silt and Clay but it also has organic material such as living microbes or decomposers and non-living organic material like decomposing leaves and animal waste soil is also full of empty space and we call this pore space por space is so critical because it allows oxygen and water to fill the soil and that allows plants roots to have access to these two things that they need in order to grow now that we've reviewed the components of soil let's take a look at how it forms the
• 03:30 - 04:00 inorganic or mineral components of soil come from the weathering of rocks so what happens is over time the force of the rain and the freeze thaw cycle of water breaks the Rocks into smaller and smaller pieces now we call the rocks that these pieces came from parent material so there's another reason not to call soil dirt it has parents after all how would your parents feel if someone called you dirt but remember that soil is more than just broken up bits of rock if we look at different layers or Horizons that a well-developed soil has we can see that the very top layer is actually organic matter now we
• 04:00 - 04:30 call this the O Horizon because it's filled with organic material like decomposers plants roots and partially decomposed biomass such as Dead Leaves or other plant matter then we have the a horizon which is also referred to as the top soil now this is a really critical layer of the soil because it contains both organic matter and mineral components of soil so it's going to contain the nutrients like nitrogen and phosphorus as well as the water and oxygen in its poor spaces all of which are crucial to supporting plant growth then there's the B Horizon which we sometimes call subsoil this Horizon is going to contain very little organic
• 04:30 - 05:00 material but it still holds a lot of the nutrients that a plant needs to grow and then finally we have the sea Horizon which contains the rocks of the parent material that have undergone very little weathering because of how deep they are in the soil and the final thing we need to go over when it comes to soil formation is the difference between weathering and erosion while weathering is the breakdown of rocks into smaller and smaller pieces erosion is the movement of those Rock Pieces by the wind and the rain now erosion is a natural process but it can be worsened by human activity and it can degrade soil soils see when erosion carries away
• 05:00 - 05:30 some of the top soil in an area it removes a lot of the nutrients and the microorganisms and bacteria in the area that are so vital to plant growth another reason that the erosion of soil is so problematic is that soil is a really good groundwater filtration system see when it rains precipitation hits the soil and begins to seep down through the pore space or infiltrate the soil as this water makes its way down through the layers of the soil many of the pollutants that it's carrying are actually trapped by the soil allowing clean water to make it all the way down to our o aquifers and recharge our
• 05:30 - 06:00 groundwater with uncontaminated water this essentially filters the water recharging aquifers and other groundwater sources with clean drinking water that's very vital for humans so now that we've covered how soil forms and why you shouldn't call it dirt we need to take a look at some of the properties that influence its fertility or its ability to support plant growth the first property we would need to review is soil texture or the percentage of sand silt and clay that is soil is made up of the reason this is so important is that these three particles have vastly different sizes which give the soils that they make up vastly
• 06:00 - 06:30 different characteristics now sand is the biggest particle by far followed by Sil and then Clay is the smallest now because bigger particles can't pack as tightly together particles of sand have much larger spaces or pores between them so a soil with more sand will have larger pores and those larger pores will allow water to drain through the soil more easily on the other hand a soil with more clay will have much smaller pores and will not allow water to drain through nearly as quickly so we call this ease or the speed with which water can move through a soil per permeability
• 06:30 - 07:00 and the opposite of permeability is water holding capacity so a soil with larger pore space that's highly permeable will have a really low water holding capacity and vice versa now in terms of water holding capacity and permeability most plants need sort of a Goldilocks level of permeability if a soil isn't permeable enough due to tightly packed clay particles with small pores water will infiltrate really slowly now the soil will also hold so much water that it can drown the plant by preventing the roots from accessing oxygen but on the other hand it for soils too permeable due to lots of sand and large large por space then the water
• 07:00 - 07:30 drains through too quickly the plants Roots can't have access to the water before it drains through the soil and into the groundwater deeper so soils with a mixture of sand silt and clay and a more intermediate pore size allow enough water to be held for the plant but not so much water that it drowns The Roots now we can measure and quantify a soil's texture by measuring the percentage of sand silt and clay in the soil and using What's called the soil texture chart sometimes called the soil texture triangle so if you collect a soil sample and set it in a jar of water overnight what will happen is it will separate by density then you can measure
• 07:30 - 08:00 the depth of each layer so you can find where the percentage of sand Sil and Clay would intersect on this chart so if we use this soil sample as an example we can see that 20% clay 35% Sil and 45% sand make this soil a loone now we can also have silty looms or Sandy looms which kind of sounds like a fire Indie band name but a true Loom is a great example of this Goldilocks level of permeability that I mentioned earlier so in addition to these physical properties like permeability or Texture soil also has chemical properties that are really
• 08:00 - 08:30 important for determining how plants can grow in it a great example of a chemical property of soil is soil PH remember that pH is a measure of acidity or basicity so the lower the pH of the soil the more acidic it is what that actually means is that it has a higher concentration of H+ ions now you don't need to remember key pH ranges of soil but what you should know is that when soil PH goes down or when soil becomes more acidic it can be degraded in two key ways first acidic soils have lower nutrient levels this is because at lower pH levels or higher acidity levels the
• 08:30 - 09:00 soil has a higher concentration of H+ ions and these H+ ions leech nutrients like nitrogen or calcium out of the soil since plants need these nutrients in order to grow this can stunt or stop their growth altogether and second acidic soil can actually damage plants Roots directly by making toxic metals like aluminum more soluble in the soil so at lower pH levels this increase in H+ ion concentration allows naturally occurring aluminum in the soil to dissolve more easily this means that the aluminum is more free to enter plants
• 09:00 - 09:30 Roots which damages them and limits their growth so we know soil pH is critical to determining plant nutrient levels but what about the actual nutrient levels themselves nitrogen and phosphorus levels of a soil are two additional chemical properties that are really important to determining plant growth and that's because nitrogen and phosphorus are usually the two biggest limiting factors for plant growth in any ecosystem now all of these chemical and physical properties of soil come together to determine something called a soil's fertility or its ability to support plant growth we don't
• 09:30 - 10:00 necessarily assign a number for soil fertility but factors such as high nutrients would make a soil more fertile while factors such as a low PH or acidic soil would make it less fertile and since this is a really complex topic with lots of interweaving concept and nuances don't do yourself dirty and just assume you have it down so stop the video now and see if you can fill out the chart for topic 4.3 in your ultimate review packet it's a great way to test yourself and see if you really have these Concepts down so continuing our path outward from Earth's core to tectonic plates to the soil we now Ascend into the atmosphere and take a
• 10:00 - 10:30 look at its different layers now remember that the atmosphere is mostly nitrogen at around 78% but that nitrogen exist as into gas molecules that aren't biologically available until nitrogen fixation occurs which converts them into a usable form like ammonia next we have oxygen at just under 21% then argon at just under 1% and after that there are a bunch of Trace gases that make up the final 0.4% of the atmosphere now it's important to point out here that even though greenhouse gases like methane and carbon dioxide make up just a small
• 10:30 - 11:00 fraction of a percent of the entire atmosphere their ability to trap heat means that even a tiny increase in their concentration can dramatically alter Earth's climate next we'll take a look at the layers of Earth's atmosphere for each layer we need to know one or two key Concepts as well as the temperature altitude relationship with that layer first we have the troposphere which is the layer closest to Earth this is where weather occurs and where the air that we breathe comes from now you can remember that the troposphere is the layer closest to us instead of memorizing it if you look at the prefix tropo tropo means change and so you can think of the
• 11:00 - 11:30 constantly changing weather that occurs in the troposphere next we have the stratosphere which you can remember is the second layer since it starts with an S it's also the layer that saves us from the Sun now this is because of the dense concentration of ozone molecules in this layer that absorb UVB and UVC rays that can mutate our DNA or cause cancer or cataracts then we have the mesosphere which you can remember is the middlemost layer because it starts with an M the key thing to remember here is that the gas molecules are becoming less and less dense as we get further from Earth's surface next we have the thermosphere
• 11:30 - 12:00 which is the hottest layer of Earth's atmosphere because it receives the most direct solar radiation this is also the region where the aora Borealis or the Northern Lights occur this is because protons and electrons blown toward Earth by solar winds collide with nitrogen and oxygen in Earth's atmosphere and give off an array of colored light and finally we have the exosphere which is the outermost layer of Earth's atmosphere and it's essentially the space that's merging with outer space now two key trends to understand about the layers of Earth atmosphere is that at each successive level we have less and less densely packed gas
• 12:00 - 12:30 molecules and at each successive level we have an opposite temperature altitude relationship from the layer below now we're not going to go into the physics of why each layer of the atmosphere has a different temperature altitude relationship but the way you can remember this is that the troposphere the layer closest to Earth gets colder as you go up an altitude just think about climbing a mountain and how much colder it gets when you get further away from Earth's surface then you can figure out the temperature gradient of any of the layers above by just reversing that relation ship at each excessive level
• 12:30 - 13:00 now that we've covered all the different layers of Earth's atmosphere we need to head back down to the troposphere and review global wind patterns as they occur at Earth's surface but before we take a look at how air circulates across Earth's surface we need to establish a few Key properties of air so that we remember why air behaves this way instead of just memorizing wind pattern directions the first key property is that warm air holds more moisture than cold air the second key property is that warm air rises third as air rises it experiences less pressure so it it cools and finally the fourth key
• 13:00 - 13:30 characteristic we need to remember is that water vapor in the air condenses when that air cools now let's start at the equator and take a look at how all of these properties combine to give us a circulation of air that we call the Hadley cell because the sun's Rays strike the equator most directly the air here is warmer than anywhere else on Earth and it holds more moisture this warm air rises and as it rises it expands and cools that causes the moisture to condense and fall as rain that air then continues to rise and cool as it experiences less pressure but
• 13:30 - 14:00 because warm air is continuously Rising beneath it it starts to spread out eventually sinking back down to Earth around 30° north and south now because this air has lost most of its moisture and is sinking back down to earth 30° north and south are going to experience very dry high pressure conditions in fact this is where we see a lot of Earth's deserts forming and it's because of this Hadley cell now since this warm air at the equator is continually being heated by the Sun and continually Rising away from Earth's surface the the equator experiences really rainy low
• 14:00 - 14:30 pressure conditions and since we know that air moves from high pressure to low pressure we're going to see this air sinking back down to Earth At 30° north and south flowing back towards the equator from high pressure to low pressure now if you're following along really closely you might be thinking wait a minute Mr smees air doesn't just flow directly from 30° north and south to the equator and you'd be completely right between 30° north and south and the equator air is moving along Earth's surface back towards the equator but there's just one issue here as that air times to move in a straight path the
• 14:30 - 15:00 Earth beneath it is spinning at almost 1,000 M hour so the air between 30° in the equator is actually deflected from east to west since the Earth is spinning from west to east beneath it this gives us the Eastern trade winds or the easterly in this region of Earth uh wait a minute uh bruh Mr SME why do the arrows change direction from 30° to 60° ah an excellent question from a very real high school student it's because the surface rotation speed of Earth is different different at different latitudes because the Earth has such a
• 15:00 - 15:30 larger circumference at 30° than it does at 60° the earth's surface is moving much faster at 30° than it is at 60 like 380 mph faster that means as air moves out towards 60 from 30° north or south the Earth begins spitting more slowly beneath it causing it to be deflected with the direction of earth spin from west to east now on topic 4.6 we'll be descending from the atmosphere back down to Earth's surface where we'll be taking a look at watersheds remember that a water shed is just an area of land that
• 15:30 - 16:00 drains into one central body of water I like to help my students visualize this by picturing it as a giant land funnel meaning that if a drop of water falls anywhere in a watershed eventually the topography or the slope of the landscape will cause it to run off into that central body of water now watersheds have some key characteristics that determine both the movement and quality of water in them slope is a really important characteristic of a watershed because it actually separates one Watershed from another so if a water droplet were to fall on either side of this dotted Ridge it would be in a different Watershed and it would run off
• 16:00 - 16:30 into a different body of water slope also helps determine how much of precipitation in Watershed can hit the soil and infiltrate into groundwater beneath versus how much flows across the surface as runoff the steeper the slope the less chance that water has to infiltrate the soil and the more likely it is to run off across the surface of the slope vegetation and soil type also play a big role in determining the quality of water within a watershed the more vegetation or the more permeable soil that you have in an area the more water can filtra into the groundwater
• 16:30 - 17:00 and the more pollutants that can be filtered out of it by that soil and by those plants Roots if we look at our Watershed diagram we can also think about how land use impacts water movement and quality in the Watershed see when runoff hits large areas of vegetation like this Forest here it's going to be absorbed by the trees roots and infiltrate into this more permeable soil but if we look at this urban area with all of its pavement and other impermeable surfaces it's going to be causing a lot of the rain water that falls here to become runoff this might be water flowing into storm drains or just into this River directly which is a problem because Urban pollutants like
• 17:00 - 17:30 sediment plastic motor oil or lawn fertilizer can flow into the river with that runoff now on topic 4.7 we'll review Earth's seasons and we have to leave Earth all together and start 93 million miles away with the Sun the amount of the sun's Rays or the solar radiation that an area on Earth receives is called insolation and it's one of the main reasons for the seasons we measure insulation in Watts a unit of energy per meter squared a unit of area now that we've reviewed what insulation is is we have to look at why it varies across
• 17:30 - 18:00 Earth's surface for a number of different reasons the first is the curvature of Earth's surface relative to the angle of the sun's Rays areas close to the equator receive much more direct radiation at a near perpendicular angle this concentrates the amount of solar energy on a smaller area which increases insolation areas at higher latitudes further away from the equator are going to receive Less Direct solar radiation because the sun's rays are striking at a more oblique angle this means that those rays are spread over a larger surface area because of the curvature of the Earth's surface another factor that
• 18:00 - 18:30 causes higher latitudes to receive less insulation is the amount of atmosphere that the sun's Rays pass through again because of the curvature of the Earth at higher latitudes the sun's Rays have to travel through more atmosphere which causes a lot of the solar radiation to be scattered by all the gas molecules that make up the atmosphere now we'll review how seasons on Earth work which is a major source of confusion for ape students every year the key to the seasons is to remember that they happen due to Earth's Tilt not the Earth getting closer or further away from the Sun so remember that as the Earth orbit the sun it's tilted at about 23.5° on
• 18:30 - 19:00 its axis this means that at certain points in the year the Northern or Southern Hemisphere will be tilted closer to the Sun than the other this causes the hemisphere tilted closer to the Sun to experience summer while the hemisphere tilted further away from the Sun experiences winter so let's review by walking through a detailed diagram of Earth's Tilt relative to the Sun at each of the four seasons we'll start with summer in the northern hemisphere which begins on the summer solstice or June 21st at this position the northern hemisphere is tilted maximally towards the Sun Sun this means that it's receiving a more direct or a more
• 19:00 - 19:30 perpendicular angle of solar radiation this more direct insulation is what makes Summer warmer this tilt towards the sun also makes this the longest day of the year in the northern hemisphere meanwhile all of this is the opposite in the southern hemisphere June 21st is their shortest day of the year and the beginning of their winter as they're tilted away from the Sun and receiving Less Direct insulation something else to point out here is that the sun's rays are hitting most directly at 23.5° north latitude which we call the Tropic of Cancer now as we progress from Summer to fall in the northern hemisphere we reach
• 19:30 - 20:00 the September equinox anywhere from September 21st to 24th at this position the Earth's Tilt is basically positioning the Earth parallel to the Sun so both hemispheres are equally exposed to the sun day length will be roughly equal at each relative latitude in the northern and southern hemispheres and the sun's rays will fall most directly on the equator as we make our way over to the December Solstice on December 21st we're now in winter in the Northern Hemisphere and summer in the southern hemisphere everything that we reviewed during the June Solstice is now
• 20:00 - 20:30 occurring for the southern hemisphere the southern hemisphere is maximally tilted towards the sun it's the longest day of the year in the Southern Hemisphere and the shortest day of the year in the Northern Hemisphere and just like 23.5° north latitude receive the most direct insulation during the June Solstice 23.5° South is going to receive the most direct insulation during the December Solstice we call this latitude the Tropic of Capricorn and finally we have the Spring Equinox in the northern hemisphere on March 20 or 21st and all the same conditions from the September equinox apply here equal insulation
• 20:30 - 21:00 reaching both hemispheres the equator receiving the most direct sunlight and equal day length in both northern and southern hemispheres now on topic 4.8 we need to go back down to Earth's surface so we can review how geography can influence climate specifically we'll be looking at how proximity to a large body of water or a mountain range can alter the temperature and precipitation patterns in a region the first thing we need to review is that when prevailing winds move across a body of water and onto a body of land they carry a lot of moisture in that air picked up over the the body of water and that's because as this mass of air is moving over the body
• 21:00 - 21:30 of water a lot of that water is evaporating from the ocean or the lake that the air is moving over to and it's transporting into the air so if we look at the Great Lakes region where I'm from we can see that the area of land just each of each Great Lake experiences what we call a snow belt now these areas receive especially high amounts of snowfall because the prevailing winds in this region move from west to east picking up moisture from the great lakes and then depositing that moisture as snow when they move over land now if we zoom into Michigan more specifically we can see just how pronounced this lake
• 21:30 - 22:00 effect snow or this snow belt is as the prevailing winds move in from the West they pick up tons of moisture from Lake Michigan and when that air mass hits land it cools down remember that when air cools it can't hold as much moisture so that moisture condenses and falls in precipitation in this case snow and you can see just how much this snowfall tapers off as we move from west to east across the state this is because that air mass coming in off Lake Michigan has less moisture left after snowing so much on the western portion of the state now Michigan's pretty flat but what happens
• 22:00 - 22:30 when we introduce a mountain range to the equation this pattern of high precipitation along the coast and less precipitation forther Inland is still there but it's way more pronounced when we have a mountain range present so as the prevailing winds come in off the ocean they're carrying all of that moisture they picked up from the water now as this air mass hits the windward side of the mountain or the portion that faces Into The Wind that air rises and cools and remember that as air cools its moisture has to condense and fall as precipitation this means that the windward side of the mountain receives a ton of rainfall and often supports Lush
• 22:30 - 23:00 thriving forests now as that air mass goes over the mountain and starts to descend down the leeward side or the side of the mountain facing away from the wind it's much drier this is because it lost so much of its moisture as precipitation on the windward side so this creates really Aid or dry conditions and often leads to deserts forming on the leeward side of the mountain now we call this pattern of precipitation that forms along mountain ranges the rain shadow effect and that's because the clouds that form as this precipitation Falls cast a shadow on this windward side of the mountain now if we go out west and look at California
• 23:00 - 23:30 Sierra Nevada mountain range we can see a perfect example of the rain shadow effect the western side or the windward side of this mountain range receives much more precipitation than almost anywhere else in the region well the leeward side on the other hand experiences some of the driest conditions in the whole country the Mojave Desert and Death Valley are two perfect illustrations of just how dry the leeward side of a large mountain range can be so now that we've covered the atmosphere the soil beneath us the Earth's core all the way at the center we need to cover the final frontier of earth science which is the oceans in
• 23:30 - 24:00 topic 4.9 we'll review a unique ocean phenomenon called the El Nino Southern oscillation or Eno the first thing we need to do is establish where Eno occurs and this is the tropical or equatorial Pacific Ocean the other thing we should establish is why it's called Eno the key is to remember that it's an oscillation or an alternation between two extremes on the one end of the spectrum we have the elino conditions on the other end of the spectrum we have the linia conditions with normal Oceanic circulation in the middle so before we
• 24:00 - 24:30 can take a look at what happens during an alino event or linia event we have to take a look at how the ocean circulates normally in this region on Earth so normally in the equatorial Pacific trade winds blow warm surface waters from east to west bringing warm temperatures low Press air systems and lots of rainfall to Australia and Southeast Asia because this warm surface water is being blown away from the coast of the Americas cold oxygen rich and nutrient-rich Waters are going to move up to the surface to replace those warm surface waters we call this process upwelling this makes
• 24:30 - 25:00 for colder drier conditions along the coast of South America but it also makes for really productive Fisheries aquatic species living near the surface are getting more access to oxygen and nutrients and fishermen are benefiting from larger catches due to this upwelling now we call this balance between the warm surface waters and the colder deeper waters the thermocline in normal conditions the thermocline tilts from east to west meaning that in the East cold ocean water is rising up to replace the warm surface water that's blowing towards the West now in an elino
• 25:00 - 25:30 year these Eastern Trade Winds weaken and even reverse directions in some instances this results in the warm surface waters pooling up along the coast of South America instead of over in the west near Australia and Southeast Asia this basically flips the normal weather patterns that we just talked about so South America is now getting the warmer weather the low pressure systems and the higher than average rainfall unfortunately this can lead to flooding and landslides southeast Asia and Australia meanwhile are receiving colder drier than average weather which can bring about drought like conditions
• 25:30 - 26:00 the other issue that this creates for South America is a suppression of upwelling meaning that their Fisheries suffer from warmer water and a lack of oxygen and nutrients this is going to result in a flattening or a leveling of the thermocline this keeps warmer surface waterers near the top colder deeper waters near the bottom and leads to generally warmer temperatures in this hemisphere now in a l year the Eastern Trade Winds have been reestablished and even intensified we have greater than normal movement of warm surface water to the west and this results in warmer than
• 26:00 - 26:30 normal weather and higher than average rainfall in Southeast Asia and Australia now Australia and Southeast Asia may be the ones experiencing flash flooding South America on the other hand experiences colder and drier conditions than normal which can cause droughts in the coastal regions especially but on a positive note these stronger than normal trade winds are blowing more of the warm surface water Westward which creates a stronger upwelling along the coast of South America this leads to a steeper thermocline and brings up more of that cold deep ocean water that has more oxygen and nutrients to support the
• 26:30 - 27:00 fisheries and there you have it four units down only five to go before you become one with the Apes Universe we've Unearthed some of the mysteries of soil Broken Ground on plate tectonics and ascended into a higher level of understanding of the atmosphere all right all right I'll stop thanks for tuning in today ape Scholars and as always think like a mountain and write like a scholar