Presentation on theme: "Getting the Dirt on Soil Soil Study Getting the Dirt on Soil For a fun internet site see:"— Presentation transcript:
Getting the Dirt on Soil Soil Study Getting the Dirt on Soil For a fun internet site see: http://www.nrcs.usda.gov/feature/education/squirm/skQ1.html
SOIL What you need to know about SOIL a) soil provides the support and nutrients necessary for plant growth; b) topsoil is a natural product of subsoil and bedrock; c) rock, clay, silt, sand, and humus are components of soils; and d) soil is a natural resource and should be conserved.
Well it is this stuff. You have seen this stuff before, haven’t you? “Yes I have! It’s dirt, right?” No, it is soil. Dirt is what you find behind your ears.
What’s the difference? We know that you spend a lot of time in the soil, so for you, there is probably not much difference. But for the rest of us, dirt and soil are very different.
Soil is the stuff plants grow in and earthworms live and without it, there would be little life on earth. We are your friends!
I love plants and earthworms. So I must love soil too. That’s nice Bob, but can we get on with it?
Rock of all different shapes and sizes Soil is a mixture of different things Boulders Rocks of different types Gravel
Things that were once part of organisms including all the yucky things like: Dead stuffDungand
Another thing that makes up a part of our soil is
Soil is also full of stuff that is alive. This stuff includes the bacteria and fungi that make the soil their home. Soil Fungi Soil Bacteria
Soil can be Divided into two Main Parts The Organic Part The Inorganic Part Organic means coming from living things (sounds like organism doesn’t it?) Putting the prefix “in” on the word “organic” makes INorganic mean “not coming from living things”
Lets start by looking at the INORGANIC part of soil
As we explained, Bob, this part all comes from the rock that forms the earths crust. I see, the earth is a big pie with a crust
Well, sort of Bob. It is like a fresh pie a few minutes after coming out of the oven. It has a cool, crunchy crust that is hard and can crack, and it has a hot squishy inside.
Here is what the earth looks like inside. Hot and Squishy Cool and crunchy
Here is a place where new rock is formed when magma (the hot squishy stuff) comes through the crust. Here is another
The rock that is formed this way looks like this.
As the lava cools it hardens into new rock. This is an example of volcanic rock.
So now that we have the earths rock crust, we have the basic stuff that soil is made of, rocks.
Here a good example of a rock that will some day be completely ground down to form soil. You can already see it at work. Where do you think all this red soil came from?
I really get it now, Nature starts making dirt with large rocks like this. large rocks like this.
And even this I think you may be starting to get it, Bob
Over millions of years mountains are broken down into smaller and smaller pieces. Mountains become boulders, boulders are crushed, cracked or split into rocks, rocks into gravel, gravel into sand, sand into silt, and silt into clay.
But how do such big rocks become soil? The forces of nature do it every minute of every day. It is called
Forces like: Water including rain, snow and iceWater including rain, snow and ice WindWind Heating and coolingHeating and cooling Earth movementEarth movement Chemical actionChemical action Plants and other organismsPlants and other organisms
Let’s look at what water does to rocks Here water looks peaceful. But it is really a very powerful force.
What happens when rocks are pounded by even drops of water?
Water is so good at destroying rock because many rocks are made of things that water is good at dissolving. Things like salt and minerals like calcium are melted by water.
Water is also a great rock crusher in its solid form. Ice splits and crushes rocks with ease.
Large rivers of Ice -- Glaciers -- move slowly across the cold areas of the earth. As they move the grind huge stones into sand and powder.
Plants and animals are constantly breaking rocks into smaller and smaller pieces. The roots of this tree are breaking the rock from its “parent” rock below it, just like a tree can crack a sidewalk.
Here you see an animal crushing gravel beneath its feet!
And, believe it or not, the internal movement of the earth is crushing rocks as you stand here now!
Remember the earth is like a hot pie. The crust sits on hot swirling goop called magma, and the crust is all cracked! In fact, there are cracks in the earth’s crust everywhere. Just look at this map.
In addition to these large cracks, there are thousands of smaller ones. The area inside the cracks is called a tectonic plate. The Pacific plate
These tectonic plates move all the time. In fact, scientists know that at one time all the continents were one big continent called Pangaea. You will now see how movement of the plates pulled the continents apart over billions of years. Keep in mind that they are still moving.
As the plates move, they either: create new rock as we already sawcreate new rock as we already saw crush rockcrush rock move rock – we call that an earthquakemove rock – we call that an earthquake
In some places the plates pull apart, in some places they come together, and in still others the slide across each other. This is a divergent fault This is a convergent fault This is a transverse fault
This is a divergent fault This is a convergent fault This is a transverse fault With this type of fault, new land is made With this type, rock is crushed or changed and mountains are pushed up. With this type of fault, earthquakes happen and a lot of rock is ground up.
Now lets look at the stuff in soil that came from living things
Soil is different in different places and depending on how far beneath the surface you go. To get a picture of this, scientists look at “soil profiles.”
All kinds of stuff becomes part of the soil. Living things that have died and decomposed, including bodies, teeth, bones, leaves, branches, grass clippings – basically anything decomposers will eat – we call things they will eat, biodegradable Poop, and all the other yucky stuff that animals produce All kind of biodegradable garbage – old hamburgers, banana peels, moldy bread, and so on.
People even use this process to help get rid of stuff while helping the soil, for example: This lovely composted manure (cow poop) will be spread on a farmers field once it is dried out. It will improve the soil without chemicals. This is part of ORGANIC farming! This lovely composted manure (cow poop) will be spread on a farmers field once it is dried out. It will improve the soil without chemicals. This is part of ORGANIC farming! (We do the same with people poop!)
One last thing and we are done. We need to know what a Soil Profile is.
A soil profile is a cross section of the soil in a particular place at a particular time. Scientists have names for each layer in the profile.
Humus layer Topsoil – thickness is different in different places Sub-soil – thickness is different in different places Weathered PARENT material – ground up rock UN-Weathered PARENT material – bedrock – earth’s crust
It is important to understand that in an undisturbed soil profile The top layer, the humus/top soil, is the NEWEST The deeper you go, the farther back in time you go
Mr. Wormy and his squiggly friends want you to see what happens to soil when you don’t take care of it, when you let it erode, and kill the plants, and use it all up.
Think soil isn’t important? Ask these kids whose father’s farm turned to a Dust Bowl, what they think!
During the Great Depression – late 1920s and the 1930s – poor soil management and a drought lead to what is called the “DUSTBOWL” Soil eroded, crops died, and people suffered.
When the Soil turned to dust, farmers in American had to leave their homes and try to find greener pastures.
Mr. Wormy says remember to say thanks to worms and humus for making your life possible.
Review 1.What is soil made from? 2.What forces grind rock into smaller and smaller pieces? 3.What is Weathering? 4.Which is made of the largest particles and the smallest: Silt, Clay, Sand? 5.What is Humus? (hint: you don’t eat it on pita) 6.What is bedrock? 7. Why are decomposers like earthworms important to the soil? 8.What do plants get from soil? 9.What is a soil profile? 10.What is a Natural Resource? 11.Why must we conserve natural resources?