Milestone 1

Reading:  Water, Water, Everywhere

Water is everywhere on Earth. About seventy percent of the surface of the Earth is covered by water. If you were an alien visiting the planet, you would see a giant blue sphere from space (especially on the Pacific Ocean side). Not only is water everywhere, but all life depends on water. The tiniest bacteria and the largest dinosaurs have all needed water. The hydrosphere is the world of water that surrounds all of us. 

Because water is so important, it makes up an entire section of the earth sciences. You will probably hear the term "hydro" many times. The prefix “hydro” has origins in ancient Greek. You will learn about hydrologists that study water and the way it is used and circulated across the planet. Hydrology is the study of water. That water may be at the bottom of the ocean or in clouds found in the atmosphere. Anything related to water is a part of the hydrosphere. 

Importance of Liquid Water

Water is in the air, on the land, between the rocks, and in every living thing. Water, in its purest form, is the compound H2O. There are two hydrogen (H) atoms bonded to one oxygen (O) atom. Generally, you won’t find pure water. There are usually other compounds, ions, or particles mixed with water. While water may move and carry other substances with it, you need to remember that the small water molecules are the things that make life on Earth possible. 

Liquid water makes the Earth a special place. Our planet has a very nice temperature range that allows water to remain in a liquid state. If we were a colder place like Pluto, all of the water would be permanently frozen and solid. On the other hand, if we were on a very hot planet, all of the water would be in a gas state. Water vapor and solid water are relatively useless to the organisms of Earth. 

Things get interesting when you start to have a system with solid, liquid, and gas states of water. Because all of the states exist on Earth, they are all important to scientists. There are solids in the deep glaciers, liquids of the oceans, and the vapor state of clouds. While there might not be a lot of life in or on those glaciers, they will eventually melt. Once they melt, they start to affect all of the life on Earth. All of the physical states are equally important because they are all connected.  

The Life of a Water Molecule

Let’s say you're a water molecule. For this example we’ll assume you are staying a water molecule and not combining with other compounds. We’re going to have you move through the hydrologic cycle. You’ll start by sitting on the surface of the Pacific Ocean. All of a sudden you are filled with energy, evaporate, and move up into the atmosphere. 

Winds are moving and you see yourself flying over the ocean towards land. Things start to get cold and all water vapor around you begins to condense. You all clump together and now you’re too heavy to stay in the clouds. You fall to the surface in a raindrop. If you are one of the first drops to fall, you might be absorbed into the soil. If you are at the end of a storm, you might wind up in runoff and drain into a river. From that river you could flow all the way back to the ocean and start your journey over again. 

How much time does your journey take? Scientists think that if you are lucky enough to evaporate into a cloud, you spend about ten days floating around the atmosphere. If you're unlucky enough to be at the bottom of the ocean, percolate into an aquifer, or get stuck in a glacier, you might spend tens of thousands of years without returning to the hydrologic cycle. As of 2013, the oldest ice ever found was about 800,000 years old. That’s a long time to stay out of the water cycle.  

Where is Groundwater?

Groundwater is water that is under the ground. Okay. You're done with the tutorial. If you want more, you should know that groundwater is extremely important. Civilization gets most of its water from groundwater sources. There is more groundwater under the surface of the Earth than in all the lakes and streams put together. Unfortunately, groundwater is also polluted more than any other source of fresh water. 

How It Gets There

Groundwater starts life on the surface. When it rains and the water moves through the soil, it's called infiltration. The area near the surface of the soil is called the zone of aeration. There are spaces between the dirt and rocks that allow the water to flow through easily. Eventually the water makes it to rocks where scientists say it percolates deeper into the Earth (yes, like a coffee pot). The area where the water winds up is called the zone of saturation. Different from the soil, the zone of saturation has very small spaces between the rocks. The spaces are so small they may even be the size of large molecules. 

When the water can go no deeper, it creates an aquifer. An aquifer is an underground reservoir inside the rocks. When a farmer digs a well, they are digging into an underground aquifer. After they drill to the water table (the highest level of the aquifer), they are able to pump the water to the surface. As farmers pump too much water out of an aquifer, they find that the water table dips in that specific area. That dip in the water table is called a cone of depression.

Aquifers

We're talking about humans pumping water out of an aquifer. There are two kinds of aquifers. One type you need to pump the water out of and another type in which the water is under pressure and moves towards the surface by itself. The pumping type is called unconfined. It has a layer of permeable(water can pass through) rock on top and nonpermeable (nothing can pass through) rock on the bottom. The water does not build up any pressure because it can expand and contract. The second type of aquifer is confined and called pressurized. It is sandwiched between two nonpermeable layers of rock. There is nowhere for the water to go when new water comes in and the pressure builds. The water eventually pushes up to the surface and creates springs and a type of freshwater called artesian water. 

Freshwater Biomes

Let's start with standing freshwater biomes, from a river to a lake or pond. The water doesn't move very quickly here. It gives animals a chance to grow up. You'll find larger fish, insects, and plants in this lake. Scientists divide lakes into two major levels, limnetic (the top), and profundal (the deeper part). They even have names for the shore (littoral) and the very bottom on the floor of the lake (benthic). You'll find most of the activity in the limnetic zone. Fishermen often fish in the limnetic zone. 

Salty And Fresh Water Mixing

Estuaries are the regions where the freshwater meets the saltwater. They will always be found near the coast. Fresh and saltwater mix constantly in estuaries. This mixing allows huge amounts of marine life to exist. It turns out that this is a great area for fish to lay their eggs. The water is quiet and still and when the fish are tiny, they can hide in the cloudy (brackish) water. When you look around you will see all sorts of birds such as cranes and storks and insects who lay their eggs near the still water also. 

Right Around The Coasts

The intertidal zone is where the waves hit the coast. Tides are controlled by the gravity of the Moon. The Moon causes them to move up and down each day. As they rise and fall they leave a patch of coast under the water when the tide is high. The same area is dry and exposed when the tide lowers. It's usually very rocky here with lots of algae and small creatures. You can walk around when the tide is low and find sea urchins, sea stars, and all sorts of birds and insects looking for food with you. 

Next to the intertidal zones are subtidal zones. This zone is always under water along the coasts of continents. You can find coral reefs and most of the world's fish in this region. You'll also find larger fish because they have more room to swim and more little fish to eat. There are also huge sandy plains in this subtidal region. Because of all of the waves and activity, there is a lot of oxygen in the water to support the wildlife. 

Deep In The Ocean

There comes a point where the floor of the ocean just drops away. Now you are in the deep ocean biome. Scientists break this biome into three layers. At the surface is the euophotic zone. There is a large amount of sunlight and oxygen but very few nutrients. They all fall to the bottom of the ocean. You'll find many small organisms that are photosynthetic. As we move down, we get to the bathyal zone. The light is very dim. No little organisms are found here, just some fish who feed on the organisms at the surface. At the bottom of the ocean is the abyssal zone. This zone is pitch black, with no producers, little oxygen, extremely cold, and high pressure. There are living organisms down there. They usually feed on the dead stuff that falls from the surface layers. Then, of course, there are the predators that swim through the murky depths.