Big picture (continued)
For an earth-like planet, you’re going to need tectonic plates which move respective to each other above the mantle. There are three generic types of plate movements, which are important to us:
Earth has seven major plates (North American, Pacific, Australian, Eurasian, South American, African, antarctic), the movements of which have shaped our continents over millions of years. Try make a globe and come up with some plates and vague continent shapes on them and try move them around - come up with sketches of plate movements at 50-million year intervals to see where your present coastline came from and how it evolved.
Mountains are generally created by convergent plate tectonics or more rarely though no-less spectacularly through volcanoes (the Pacific Rim). Through the above exercise in plate tectonics, you can determine where old mountains (worn down by the elements) and new mountains (higher, more jagged) can be found. The positioning of your mountains will directly inform where river basins will be.
In its simplest term, a river basin is an area bordered by highlands and mountains, where all streams and rivers converge into a single river, which leads to the sea, a lake or another river. You can create vague river basins at this point to give you an idea where all rivers will eventually flow. This will give you a clear indication as to which is the largest river (the largest land area within an individual river basin), which might be important to a particular culture you plan on creating.
Rarely, a river basin will not lead to open water. This is what we call an endorheic basin. Basically, all rivers will lead to a particular lake that is not connected to the sea. The lake may fluctuate in size as seasons change (it may expand in winter due to floodwaters or ice melt in spring/summer, or it may shrink in times of drought). Damming of major rivers or climate change may slowly kill such a lake (Aral Sea). Endorheic basins typically have water that is more salty that larger seas (Dead Sea).
This brings me to the contentious subject of rivers, pitfall of many amateur cartographers. There are a few simple rules you need to follow when making rivers:
Some rivers have major silt deposition - they carry lots of silt along their course, which is deposited at the mouth of the river. This often creates large headlands which alter the coastline (Nile delta, Mississippi delta). Keep this in mind when designing your coastlines, particularly around large rivers. Larger deltas do not necessarily belong to the largest rivers. The Ganges river has the largest delta, is the 3rd largest river by discharge, though it is only the 34th largest river in the world. Generally, deltas are very fertile (Nile, Ganges).
A river that flows into another river is called a tributary and the ‘parent’ river is the distributary. The mouth of a river (where it flows into the sea) is the delta, and often protrudes from the coastline as sediment carried along the river is deposited there (look at satellite images of the Nile or the Yellow River). Deltas can be very fertile. Steep rivers flow faster than those with a shallower decline. Fast rivers tend to be straighter and narrower than slower ones, which are wider and more winding. Faster rivers erode the surrounding area quicker than slower rivers. Canyons are created by river erosion. Rivers rarely bifurcate, though bifurcations are common in flat deltas and wetlands.
Now our world is starting to look like a world (see part one). We can begin to position our biomes - forests, deserts, plains, etc. If you want you can also place resources at this time, as realistically, certain resources will be found in certain terrain types.
There are many biomes, which are roughly linked with climates, and I have listed the most common below, alongside a vague description of what generic flora and fauna you’re likely to find in them. Do keep in mind that biomes transition gradually from one to another, and not all species of flora and fauna are contained to the same ‘boundaries’ as each other, so 1 species might be found in grasslands and shrublands, though another might share the shrublands with it but not range as far as the grasslands.
Flora and fauna
Many world-builders like to create their own flora and especially fauna. That’s all well and good but, thinking realistically, when doing so you need ask yourself some questions (particularly if you’re adding a fantastical species): is this species replacing something or being added into the biome?
If it’s the former you obviously need to find a creature that fulfils a similar role in the ecosystem and remove it. If it’s the latter, you need to ask yourself some questions: what’s its role in the ecosystem? What does it eat? What preys on it? Is it wild or domesticated? If it’s domesticated, what wild animal is it descended from?
Keep in mind when creating biomes and populating them how wildlife is spread on earth - herds of bison and other mammals can sometimes number in the tens of thousands if not hundreds; some flocks of birds have been estimated to be in the millions; and schools of fish might even number in the tens of millions! Such large groups cannot survive in the same place for long. So remember the feeding habits of animals.
Humans exploit whatever they find, so their culture will be influenced by what plants and animals they find there. Distinctive species like elephants (ivory), lions, bananas, poppies (opium), even something as innocuous as sheep, can greatly influence an entire culture.
A common staple of fantasy stories, forests are closely linked with myths and superstitions around the world and can similarly form a basis of a fantasy world.
There are three general types of forest (technically incorrect, though for the purposes of worldbuilding, we’ll stick to those). These are:
but are rather reshaped and altered by millennia of human (and sometimes animal) influence. It is thought that as little as 3% of forests in Europe are old growth forest (commonly called virgin forest), with the remainder having been reshaped by millennia or human interference.
Key things to remember:
Atmospheric Circulation - https://en.wikipedia.org/wiki/Atmospheric_circulation
Climate - https://en.wikipedia.org/wiki/Climate
Endorheic Basin - https://en.wikipedia.org/wiki/Endorheic_basin
Genesis of common ores https://en.wikipedia.org/wiki/Ore_genesis#Genesis_of_common_ores
Koppen Climate Classification - https://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification
Plate Tectonics - https://en.wikipedia.org/wiki/Plate_tectonics
Rain Shadow - https://en.wikipedia.org/wiki/Rain_shadow
River Basin - https://en.wikipedia.org/wiki/Drainage_basin
River Delta - https://en.wikipedia.org/wiki/River_delta
Trade Winds - https://en.wikipedia.org/wiki/Trade_winds
Trewartha Climate Classification - https://en.wikipedia.org/wiki/Trewartha_climate_classification
Atmosphere of Jupiter - https://en.wikipedia.org/wiki/Atmosphere_of_Jupiter
Hadley Cell venus - https://www.seas.harvard.edu/climate/eli/research/equable/hadley.html
Number of atmospheric cells per planet - http://earthscience.stackexchange.com/questions/992/what-factors-determine-the-number-of-hadley-cells-for-a-planet
One artmospheric cell postulation - http://worldbuilding.stackexchange.com/questions/21838/what-would-the-climate-be-like-on-an-earth-like-planet-with-only-one-convection
Part One: The Big Picture
Part Three: Civilizations (13th Nov)