in this video we're going to talk about weathering erosion and deposition let's begin with some simple definitions of these three terms so weathering in this sense is the breaking down and changing of rocks as a result of exposure to the environment so if I have a large slab of granite in nature and over hundreds and thousands of years the waves of the ocean are crashing onto that rock inevitably the rock is going to break down into smaller pieces it might get rounded out it's essentially going to change as a result of exposure to its environment and that's just one example of what weathering can be there are lots of different types and we're gonna look at those in this video after rocks are weathered they are often eroded and that process erosion is the transportation of the sediments that have been broken down by weathering so if you imagine little bits of granite being pounded off of that slab because it's being hit by wave after wave and then being carried away in the ocean current to a different location well the act of carrying those little chunks of granite those weathered sediments from point A to point B that is erosion erosion is all about movement and transportation the final part of the process is called deposition so deposition is the dropping off of the sediments that have been weathered and eroded so to continue my example if those little tiny bits of granite broken off and weathered by the waves and then eroded or transported by the ocean currents eventually get deposited on a coastline many hundreds of miles away that is deposition the dropping off and so to kind of summarize this and some of the other key ideas we're going to use this surface process flow chart which is available on the website and we'll begin by filling in the three boxes on the top to kind of summarize these three main processes starting with weathering which we know is breaking a part of rock and then erosion which is the transportation of the sediments and finally deposition or the dropping off of those sediments so another way to think about this this is just kind of a quick analogy that and it helps me remember the differences between them is that weathering is like kind of like nature's hammer right its mother nature's way of taking big bits of rock and smashing them into smaller bits or changing them into something new and then erosion in this example would be something like a dump truck or a pickup truck carrying all the little bits and pieces broken apart by weathering from one location to another and then deposition is that dump truck kind of opening its tailgate and dumping everything out into a big pile on the ground - that's deposition so that's just kind of a helpful little way to remember the difference is between these three parts of this larger weathering erosion deposition process now for the rest of this video we're really going to focus on weathering specifically and we're going to start by looking at the two main types of weathering and the first example we're gonna look at is called physical weathering now I just want to point out that physical weathering is also often known as mechanical weathering okay so physical and mechanical are the same thing and this would be the breakdown of rocks into sediments and the key is that it's without changing their composition so this is literally changing size and shape of Iraq so the waves crashing against a boulder and breaking it into small pebbles that might be rounded out that's physical or mechanical weathering but it's still granted it's not changing the rock or what it's made of but that does also happen in nature and we have a different name for that that's called chemical weathering and so this is when the rocks are changed chemically because of some reaction with usually something like when air or water in nature so the altering of rocks as a result of exposure to different substances so let's add this information to our flow chart so we're breaking down weathering into two smaller types the first is physical or mechanical weathering which is breaking cracking and grinding things like that and we'll see examples of those shortly and then chemical weathering which involve some sort of reaction that changes composition so that's a really key difference between the two types of what so let's dive a little deeper into our physical or mechanical weathering and look at some different examples for our purposes we're gonna break this into four specific types frost action exfoliation abrasion and root wedging so we will start with frost action which by the way is also known as ice wedging there are a lot of different names for it and as you might imagine this involves ice and so what happens is take an area that maybe it's a little bit above freezing temperature during the day and you get some rain or maybe some melting snow and you have some water that seeps into the cracks within a rock right and then the Sun sets and inevitably the temperature drops and that water freezes into solid ice now you may know already when water freezes it expands slightly and it gets a little bit bigger and so as it expands it's going to be pushing outwards on the rock that it has seeped into and that force believe it or not is actually strong enough to very slowly and gradually break apart rocks and this process is known as frost action or ice sweating and so we see examples of this in all sorts of areas where the temperature is a little bit above freezing during the day and then below freezing at night and in fact a good example of this is what we call a pothole which you see all over the streets particularly in the northeastern United States in the springtime when you have these big fluctuations in temperature the water actually gets into cracks in the road and then freezes and expands and then you drive over it the next day and it just breaks apart and you end up with these big nasty holes in the ground that's a good example of frost action or ice sweating second would be exfoliation and this is in a way kind of similar this involves temperature changes as well so this occurs in areas where you have really dramatic temperature changes where it gets very hot during the day and then very cold at night the the rock itself will actually expand slightly in the heat and then contract in the cold and if this happens day after day night after night it weakens the outer layers of the rock until they eventually begin to crack and peel apart like this or like this right here it's almost like the rock is shedding its outer layers and physically or mechanically breaking apart largely as a result of these temperature changes a third example which is the most common and we see it all over the world is called abrasion so abrasion is basically whenever Rock grinds against other rock and it comes in many forms like here in the desert we see a lot of wind abrasion where gusts of wind will blow grains of sand that crash into other rock and very very slowly over thousands and thousands of years will actually eat away at the rock and so wind wind abrasion is actually responsible for a lot of the interesting kind of rock formations that we see in the American Southwest we also can have water or stream abrasion as little pebbles and sediments are bounced along the bottom of a stream as the water flows and that's going to eat away at the rock that they're bouncing over we also see this on coastlines as I mentioned before with waves crashing into rock and grinding it down by carrying little bits of sand and sediment and eating away at the rock and then finally with glaciers glacial abrasion is very common glaciers glide downhill pulled by gravity and they scrape along the rock and carve it away over many hundreds of years finally the last type of physical or mechanical weathering we're gonna look at is called root wedging and it's pretty self-explanatory this is when plant roots actually grow within the cracks of rock and as the plants grow larger and larger they break apart the rock as they grow into it so we see examples of this all over the world and it's amazing how powerful tree roots and plant roots can actually be so much so that they will physically break apart rocks as the plants grow so those are four main examples of physical weathering and we want to add them to our flowchart here so under our physical weathering area we're gonna add frost action which is freezing and thawing of ice is going to crack apart rocks we have exfoliation which is the alternating hot and cold old is going to crack rocks we have abrasion which is grinding of one rock against another or sand against rock and then finally root wedging which would be our plant roots growing into the rocks and so those are four main types of physical weathering now let's shift gears and look at the second type of weathering chemical weathering so remember this is the altering or the changing of rock as a result of exposure to different substances and we're going to look at two main examples of this oxidation and carbonation we'll begin with oxidation which is a term you may have heard before it's the formation of rust and this is going to occur whenever the element iron is exposed to oxygen and that can happen in the air or in the water and so what we find are that there are a lot of rocks around the world that contain large amounts of iron and as that iron reacts with the oxygen in air or water it's going to physically rust and the result is that we see rocks that look like they've been rusted they have this orange e color to them and that is actually a form of chemical weathering this rock is breaking down the rust is very crumbly this iron oxide that forms and it breaks apart the rock over time it's an actual chemical reaction with oxygen in the air or the water and then finally we have carbonation carbonation is really interesting this is responsible for the formation of these fascinating beautiful limestone caves that we see around the world and it's basically when water flows through the ground it reacts with the different materials in the soil to create a very mild acid this carbonic acid and carbonic acid is strong enough that if it encounters certain minerals or rocks like calcite or limestone it will eat away or dissolve that limestone and so what we end up getting are these underground caverns where there once was a whole large expanse of limestone but that has all been kind of eaten away slowly by the dissolving of this carbonic acid so we see some of these amazing amazing landscapes around the world formed as a result of this type of chemical weathering another thing that happens with this carbonation is that sometimes the ground will actually give way because all the rock beneath it has been eaten away and that's when we get something like this which is called a sinkhole which is when the rock is gone beneath and the ground collapses above and so those are two types of chemical weathering and again we'll summarize them on our flowchart so the first type was oxidation iron and oxygen gives you iron oxide or rust and then carbonation which is when we have this acidic rain and acidic water dissolving limestone and giving us caves okay now there are two main types of weathering with some examples of each we have them nicely summarized on our flow chart and the last question we want to ask here is so what's going to affect weathering like what dictates the type of weathering we have in a region how fast it will happen etc and so we have three main things that we're gonna look at and the first is climate the second would be hardness how hard is the rock or how resistant is it being weathered and then the third would be the surface area of the rock how much of the rock is exposed to the elements all right so let's start with climate and to understand this we look at this chart this is a very commonly used chart in geology and so what this shows is the effect of the temperature and moisture on what type of weathering will take place so for example in an area that is more hot so this part of our graph right here which is a higher temperature okay but not a lot of moisture because remember if we go up on the chart that's a wetter area so this is an area right here that's hot and dry hot and dry we don't really see a lot of weathering we might get some wind abrasion like in the desert but nothing too severe if we then switch up to an area that is higher on the chart that is hotter and wetter that's where we're gonna start to see more of this chemical weathering this carbonation occurs a lot and a lot faster in areas that are hot and wet we see a lot of limestone caves and sinkholes in a place like Florida for example where it's very warm and on the other hand if we go to the left side where it's colder lower temperatures this is where we're gonna start to see frost action happening because this is where we have a lot of change in temperature it's colder cold enough to get ice and enough water to have the ice forming and melting and forming and melting day after day anything up in this top area up here these are climate conditions that we don't really see on earth so they're not really relevant to what we're talking about anyway this this graphic gives you a really good sense of the impact that climate has on the type and the severity of weathering that happens in a particular area in addition to climate we also have to look at hardness so of course we know that all rocks are different all minerals are different some are very hard some are very soft and that's going to have an impact on how quickly they're going to weather so if we look at a diagram like this which shows a cross-section of a waterfall what we'll notice is that some of the rock layers like right in here right in here right here have been worn away more than other rock layers like this one is not worn away as much these ones down here this a little bit right here is not really worn away and that tells me that these are different types of rock and so I can conclude that this layer of rock right here which believe is like a shale is a softer Rock so when all of this water splashes up on it it's gonna start to wear away faster then a harder Rock like say a sandstone so the hardness of the Rock has a big impact on how quickly it's going to be weathered and so finally the last thing we want to look at is surface area so surface area refers to how much of the rock is actually exposed so if I have two rocks like you see here they're going to be exposed to the elements at a different clip right so the only part of this rock for example that's going to be exposed is the outside of the rock so the surface is that I'm highlighting right here that's the only part that can get hit by rain and ice and snow and oxygen etc that's the only part that can be weathered the center of this rock is not exposed its protected and therefore it's not going to be weathered whereas in the right hand side I have the outsides of these rocks but I also have these inside areas right because the rock is broken down we have exposed additional surfaces that can be hit by rain snow and ice and oxygen and other chemical reactions and so because this has more surface area the purple it's going to break down at a faster rate okay so we can summarize these three things in our large box at the bottom of the flowchart we can summarize the factors that are going to affect weathering okay so weathering is most affected by these things the climate the hardness of the rock and the amount of exposed surface area that's what's really going to dictate how quickly a rock is going to break apart so in this video we took a look at the different types of weathering along with some basic definitions of weathering erosion and deposition and then finally at what effects weathering shortly I'm going to release another video that's going to go into details about the processes of erosion transportation and deposition are dropping off of sediments so keep your eye out for those thanks for watching