WB02.2 Worlds and Planets (Seismology/Tectonics and Climatology)
After this module you will have created/generated the gross physical characteristics of your world by generating linked regions of water and land and work out overall climates and prevailing currents and winds.
Continents and seas ride on crustal plates that float on the softer, hotter material of the planet’s mantle. Their movement is almost imperceptible by human standards. Friction and collision between moving plates can result in earthquakes, volcanoes and the formation of mountain ranges to say the least.
In your fantasy world this can be caused by anything from god’s, elemental panes, magic , restless Deities etc etc whatever you feel fits your story and campaign. You can invent how your planets geology functions.
Our earth’s crust is divided up into plates, and all the continents and seas rest on top of those plates. You’ll find that the greatest seismic activity will be at the edges of the plates.
A typical earth sized world would have 4d4 plates, with each plate spanning 1d6 regions on the world map. If using this method and you run out of regions make the remaining regions a single-region plate.
The guidebook has tables for rolling up the following:
- Mountain chains and Rifts (Trench systems)
- Adjustments for Gravity World
- Volcanic Activity
- Earthquake Activity
- Geological Activity on Fantastic Worlds
Mountain chains and Rifts (Trench systems)
To use the table choose one plate and roll d% to determine movement and characteristics with the adjacent plate.
Mountain ranges are the best place to find colliding plates, and rifts are the best place to find receding plates. Mountains tend to form in chains or ranges instead of clumps with volcanoes being an exception.
Adjustments for Gravity World
If your world has higher gravity your mountains will be smaller, if you have lower gravity it will be larger. Check the size/adjustment chart if this is applicable to your world.
On Mars Mons Olympus is 80,000 feet high, compare to Everest on Earth at 30,000 feet.
Volcanic activity is the result of the planets’ seismic stress and heat, or whatever fantastical explanation you created. Other nearby moons, or celestial bodies, can affect planetary stress as well.
If you have volcanoes on your world you can roll to check for type of activity. Roll d% and refer to the table in the guidebook.
Plates can also cause earthquake activity. The table in the guidebook can help you determine the strength and frequency of the activity using d%.
Geological Activity on Fantastic Worlds
There’s an alternative if you don’t want to use plates, check the tables on Optional Regional Mountain Placement and Fantastic Mountain Properties in the guidebook. It uses d% for placement and properties.
In my world or current island location I know I wanted mountains and will adjust tectonic plates after their design. Remember these are guides based on real earth like worlds but it’s your campaign and story.
This is the last step affecting the entire planet. World climate has, for this reference, five possible categories:
These five categories create nine distinct bands of climate. Each band can have significant local variations.
The guidebook has two tables on climatology, Planetary temperature and Seasonal variations.
Planetary Temperature determines the mean temperature which can range from frozen to inferno etc. The mean temp of the planet can cause climate bands to be one or two steps higher or lower then normal. you can roll to determine the temp or perhaps you already have one in mind.
Seasonal variations can be scientific or even something out of Greek mythology. They can range Mild to Extreme or none at all.
In my current world i’m using normal for temp and variations. Although other planets in my multiverse will be adjusted later on when developed.
Prevailing Winds and Ocean currents
General rule of thumb for earth like worlds: In the Northern hemisphere currents move clockwise in motion and for the Southern hemisphere it is counter clockwise. Use the equator as a dividing line for anything that crosses over.
For wind patterns Oceans and large land masses support huge pressure cells that generate weather patterns and prevailing winds. The winds still rotate clockwise and counter clockwise like currents.