GM Like a Druid: Continents
Jess Miller-Camp (they/them), Ph.D.
Druid GM Designs
The Geology of�Middle-Earth
Serjeant, 1996;
building on earlier work
by McIntosh, 1973
The Geology of�Westeros & Essos
Zahirovic et al. 2019
Earth Systems Science
Geosphere
Biosphere
Hydrosphere
Atmosphere
Plate tectonics
Geomorphology
Soils
Petrology
Biomes
Habitats
Primary
productivity
Biogeography
Precipitation
Ocean currents
Glaciers
Drainage basins
Atmospheric circulation
The Sun’s Energy
Weather
UV filtering
Earth�Systems Science��(Elements Edition!)
Earth
Fire
Life
Water
Air
Class Structure
Break
Break
Eat, hydrate, bathroom, decompress!
Science!
Build your world, layer the information!
The Bedrock of Worldbuilding
Plate tectonics,
Geomorphology (the shape of the land), and
Petrology (rocks and minerals)
Plate�Tectonics
Map by the USGS
Plate�Tectonics
Hauptvogel and Sisson, 2023
Plate�Tectonics
Nature’s�complicated!�(don’t sweat it)
Don’t stress the details
It’s okay to handwave
Celerier et al. 2009
Plate�Tectonics
Map by the USGS
Geomorphology
Images by NPS, USGS,
MiraCosta College,
Anders et al. 2022
Divergent boundary
(continental)
Geomorphology
Images from Science Photo Library,
Woods Hole Oceanic Institute�Þingvellir National Park
Divergent boundary
(oceanic)
Geomorphology
Images by Viewfinder Panoramas,
MiraCosta College
Convergent boundary
(continental)
Geomorphology
Image by NOAA,
HMSPinaforeWithKDen.com
Convergent boundary
(oceanic)
Geomorphology
Lemenkova 2019,
Sanchez 2008,
Aheadoftheherd.com
Convergent boundary
(continental–oceanic)
Geomorphology
Images from Wikimedia
Transform fault
(any crust type)
Plate Tectonics
Images from US NPS,
Tarduno et al. 2009
Away from plate boundaries
Hot spots are isolated points of volcanism
Track plate movements over time
Crust bubbles up over hotspot, then drops as it moves off of it and cools
Volcanoes erode once they’re not being added to
Petrology
Image from
Kids Press Magazine
Igneous rocks are frozen lava/magma
Ash deposited downwind of volcanoes
Dense, dark lava that flows well at divergent boundaries and most hot spots
Lighter, less dense lava in explosive eruptions at convergent boundaries
Some rocks (including some mountains!) are old magma chambers exposed after softer rocks eroded around them
Igneous rocks
Petrology
Image from Geology In
Metamorphic rocks are rocks changed by heat, pressure, chemicals
Convergent boundaries
Cores of mountain ranges (sometimes cores are all that’s left!
Metamorphic rocks
Lots of gems
Petrology
Sediments and Sedimentary Rocks
Erosion of other rocks is mostly by water, wind, gravity
Sediments move downhill, downstream, downwind
Deposited in low-lying areas
Precipitate out of liquid, chemically or by animals
A lot of the ocean floor is covered in shelly, dead plankton
Reefs and deserts
Time for Worldbuilding Phase One!
Breaktime!
Glazing on Climate
Latitudinal temperature gradient,
Atmospheric circulation,
Oceanic circulation, and
Seasons
Latitudinal Temperature Gradient
Image modified from Vector Stock
Sun=Energy🡪Heat and Movement
More spread out=colder
Axial tilt🡪
Seasonality
Atmospheric Circulation
Image from Carlton College
Warm air goes up,
Cold air goes down
Centrifugal motion sends air
toward the equator and up
Cells at different latitudes
interact with each other
like cogs
The bigger the planet,
the more “rows” of cells
The faster the spin,
the stronger the cells
The more interruptions
(e.g., continents),
the weaker the cell
Coriolis effect deflects
winds to the west
The thicker the cell,
the more momentum
it has to affect its neighbors
Atmospheric Circulation
Image from Wikimedia
As air cools down, it gets drier, denser, and drops.
As it heats up, it gets�wetter, less dense, and rises.
Air pushing down creates high pressure.
Air pulling up creates
low pressure.
High pressure
suppresses precipitation.
Low pressure
encourages precipitation.
Winds are low where
two cells run into
or away from each other.
Winds are high inside them.
Oceanic Circulation
Image by The University of Waikato
Te Whare Wānanga o Waikato
Ocean gyres are counterparts of atmospheric cells
Constrained by continents
Take warm water north and send cold water south
Powerful, fast currents where not constrained
Water in middle of
gyres is calmer, and the expected temp
for their latitude
Westward currents at equator due to planet’s spin
Oceanic Circulation
Image by NOAA
Great Ocean Conveyer Belt
Controlled by temperature and salinity
Hot water rises.
Cold water sinks.
Less salty water rises.
More salty water sinks.
Temperature and salinity work in a positive feedback loop
Cold and salty half deeper than ocean gyres
Surface complements ocean gyres
Seasonality
The tropics are dominated by precipitation changes
Seasons are a variation in prominent abiotic aspects of the environment
(e.g., temperature, precipitation, light)
Mid-latitudes are dominated by temperature changes
The poles experience strong seasonality in light
Wind and other aspects of weather can vary seasonally, too
Image from Dirmeyer
Seasonality
Monsoonal climates (pronounced wet/dry seasons) can and do extend outside the tropics given the right conditions
Image from Dirmeyer
Generally, tropical and subtropical monsoons occur in the summer,
and temperate monsoons occur in the winter
Time for Worldbuilding Phase Two!
Breaktime!
The Waters of Life
Watersheds,
Biomes, and
Nutrients
Watersheds
Discrete regions where all the precipitation is channeled to the same place
Can be as big as “to this ocean” or as small as “to this rivermouth”
Things that happen upstream have compounding effects on downstream locations
Includes rivers, lakes, glaciers, and groundwater
Image by The Watershed Project
The fewer connections to other watersheds, the more unique the flora and fauna
Watersheds
Some watersheds don’t lead to an ocean (endorheic basins)
Evaporation is the primary mode for water to leave these
Image from Wikimedia
Biggest are called continental divides
Biomes
Groups of habitats that share major characteristics
Temperature and humidity are the determining factors
Image from Wikimedia
Biomes
Images from
DiVenere 2012, Wikimedia
“Hypothetical/Ideal/�Mean Continent”
Cold
Wet
Dry
Groups defined by dominant plant type
Biomes
Image by Halasz 2003
Altitude also a factor!
Nutrients
Life uses up nutrients, so nutrients come from the dead and places where little to no life has been active
Deep ocean sediments brought to surface by upwelling
Nutrients from the mantle brought to surface by volcanoes
Certain environments rapidly decompose things into rich soil
River floodwaters deposit sediments that used to be locked up in rock
Image from The Spruce
Time for Worldbuilding Phase Three!