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Water, Ice, Wind and Gravity


The four agents of erosion, or the transport and removal the products of weathering, are water, wind, gravity, and glaciers. *Note: water and ice are sometimes thought as one agent, making three agents of erosion total (water, wind, and gravity).

Water, whether in the form of a stream, an ocean, or even heavy precipitation, transports sediments. In the image below, the water has worn away the rock and these rock sediments have been transported elsewhere.


During wind erosion, moving sediments are picked up by the wind and are transported depending on the strength of the wind and the mass of the sediment.


Gravity also causes erosion. This process can happen gradually over time or more quickly, such as during a landslide or avalanche.


Finally, glaciers transport sediment when they move. This process occurs very slowly, but as a glacier moves across land, it picks up and distributes sediments. In the image below, you can see how the contact between the ice and the earth disrupts sediments. These sediments become trapped in the ice and moved.


As you can see in the image below, glaciers aren't just ice.


Environmental conditions do change in the oceans, but the terms climate and weather are not usually applied.


In the atmosphere, climate is longer-term changes in rainfall, temperatures, humidity, pressure, winds, etc., while weather is short-term changes (days to weeks) changes in the same factors.

in the ocean environments, temperature and pressure play important roles, but pH and salinity are also important factors. Needless to say that humidly in the oceans is not a factor as it's 100% water!

Every marine or lake organism evolves over million of years to fit into a given environmental niche. If the environment is fairly stable, the environment will continue to thrive. You can think of long-term marine environments as roughly the same as "climate" on the land. If environmental changes happen rapidly, like say El Nino, this might be analogous to weather.

During El Nino or La Nina events, vast schools of fish migrate to areas of the oceans that have the right temperature for them to thrive in. When things settle down again, they migrate back. A hurricane on land/surface of the ocean can also have big short-term impacts to the shelf regions of the oceans too - you could argue this is "oceanic weather."

Organism evolve in certain temperature/pressure/salinity conditions but when those conditions changes (like they are now with global warming) species are challenged to adapt or die out. Right now corals are struggling to adapt to longer-term changes in the ocean temperature and ph conditions, brought on by atmospheric above land climate change.


It really works the other way around: climate changes are impacting the weather.


Climate refers to the weather conditions in a particular area over a long period of time. When we discuss changes in climate, we discuss long-term changes in the natural greenhouse effect, temperatures of the oceans/land, heat content of the atmosphere, changes to pressure cells, changes to the cyrosphere (ice and snow) and a number of other factors.

Weather refers to short-term changes in air temp, pressure, wind speed and the kind of information you get in a weather report. Weather is largely driven by climatic factors (as above). So, when the climate starts to change (as it is now), the weather also gets out of whack. Global climate change right now is leading to more heat waves, more intense rainfall events and associated flooding, more intense and longer wildfires and a number of other impacts to weather systems.

Check out this related question on the difference between weather and climate.


Humans are been able to "ignore" many limiting factors due to advancements in technology and culture.


Ecological limiting factors for any population include space, food, predation, and disease. Humans are subject to these same pressures, however, we also have introduced war and pollution, though some scientists believe these can be included in the other categories.

Certain cultural and/or technological shifts have changed human population growth through history:

-Agriculture played a very important role in the history of humanity and populations exploded in size upon discovering it. This period of time is referred to as the Neolithic Revolution. Domesticating crops allowed humans to settle permanently in place and produce a surplus of food rather than move frequently to follow seasonal production patterns in the wild.

  • The industrial revolution allowed more people to live in close proximity to each other in cities while, at the same time, shrinking the population in rural areas, as agriculture became more automated and keeping food fresh for transportation purposes improved. In other words, people no longer need to live near where food was grown.

  • Advancements in medicine have allowed for people to fight off disease and survive accidents through surgery. Better understanding of how we get sick has also altered behaviors, such as better water treatment and sanitation facilities.

  • Smaller family sizes have become common. Because people are living longer (ie: not dying of disease), and families no longer need large numbers of children to work the fields (basically, free labor), people are having fewer children.

  • Education and advancement of women in society has caused women to get advanced education and degrees and stay in the workforce. This means many women are not financially dependent on a partner and can afford to get married later in life, thus limited her childbearing years, and having less children overall.


These are all different terms used to organize life on Earth. See explanation.


These are different terms used to organize life on our planet.


An organism describes an individual. You are an organism. I am an organism. The mosquito that flies by your window is an organism. An organism is a single, living thing and can be an animal, a plant, or a fungus. Organisms grow and respond to their environment.

A population is the term we use to describe multiple individuals or organisms of a single species that live within a particular geographic area. For example, there may be one population of painted turtles in one state and another population of painted turtles 250 miles away in another state.

A community is the term used to describe two or more populations of different species that occupy the same space at the same time. For example you could talk about the community of Yellowstone National Park that is made up of numerous animals such as elk, bighorn sheep, coyotes, porcupines, different species of frogs, and fish and insects and so forth.

An ecosystem is the term used to describe both the biotic (living) and abiotic (nonliving) factors in a system. The ecosystem in the image below is made up of birds, frogs, fungi, plants, mammals, bacteria, the water, the run, the rocks, the soil, and so forth.


A biome is the term used to describe organisms that occupy a certain area. Biomes are determined by the primary vegetation type, the climate of the area, and the geographic location. The plants and animals in a biome share common traits that are specific to the individual biome those plants and animals inhabit.

A biosphere is the term used to describe the combination of every ecosystem on the planet. Our biosphere is Earth. The biosphere includes all living beings and their relationships.


By acidicfication


When carbon dioxide dissolves into seawater, a portion of it creates carbonic acid, #"H"_2"CO"_3#, which in turn ionizes to form hydrogen ions and bicarbonate. The bicarbonate ions further ionize to some extent into carbonate and hydrogen ions.

The natural pH of the seas is approximately 8.1, which means it is somewhat alkaline (not acidic). The reactions that take place due to more carbon dioxide in the atmosphere (summarized above) release hydrogen ions, which make the water less alkaline.

Compared to preindustrial times, the seas have already experienced a drop in pH of about 0.1 and it is highly likely that marine pH will fall by another 0.3 by the end of this century.


If that happens, the seas will be more acidic than they have been for hundreds of millions of years. So, this will cause end of some creatures and environmental conditions.

For instance, carbonate is needed to build the calcium carbonate in shells and other body parts of marine creatures such as snails, starfish, clams, urchins and others. Read more here.

Some of the most important organisms likely to be affected by a lack of carbonate due to atmospheric #"CO"_2# buildup are certain types of plankton and small marine snails that are a major source of food for fish species and marine mammals. Coral reefs may also be impacted, since they are built from secretions of calcium carbonate by small sea anemone-like animals and coralline algae (the reefs).

Similar to the seas, rivers, lakes, and streams will suffer from increasing #"CO"_2# in the atmosphere both physically and ecologically.

References: Masters, G.M. and Ela, W. P. (2008). Introduction to Environmental Engineering and Science (3rd edition). Pearson International Education, Upper Saddle River, NJ, USA.

To learn more about ocean acidification, see this link.

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