Map Making: Weather, Biomes, & Plate Tectonics

Since we are working from an earth-like world we will assume that geological processes and water cycles work similar to earth. First you need to understand why different biomes and environments exist in different locations. It is all based on weather patterns formed by the rotation of the earth, the heating and cooling of the air and geography. We will talk about weather and plate tectonics as it relates to biomes and map making.

Understanding Weather

Weather

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1. Hadley Cells and Biome Distribution:

Equator = Rainforests: Place tropical rainforests near the equator. The rising air within the Hadley cells near the equator leads to high rainfall and warm temperatures, making this area ideal for lush, dense tropical forests.
30° Latitude = Deserts: Create deserts around 30° latitude (both north and south of the equator). The sinking air in these regions causes high pressure and dry conditions, which are ideal for desert biomes. Place deserts in both hemispheres, similar to how Earth’s deserts form in the subtropical belts.

2. Temperature Gradient by Latitude:

Polar Regions = Tundra/Ice: Towards the poles, the temperature will drop significantly, giving rise to tundra or ice sheet biomes. These are areas with very low temperatures and minimal vegetation, similar to Earth's polar regions.
Temperate Zones: Between the tropics and polar regions, place temperate forests, grasslands, and mixed biomes. These areas receive moderate sunlight and experience four seasons, which allow for diverse plant and animal life.

3. Prevailing Wind Patterns:

Trade Winds and Westerlies: Use the prevailing wind patterns from Hadley, Ferrel, and Polar cells to decide rainfall distribution and climate effects:
- Trade winds (from the east near the equator) help guide moisture toward the equator, contributing to rainfall.
- Westerlies (in the mid-latitudes) bring more temperate climates and can distribute rain and storms over landmasses.
- Rain Shadow Effect: If you have mountain ranges near deserts, use the rain shadow effect. Mountains facing the prevailing winds will have more rainfall, while the leeward side (facing away from the wind) will be drier—potentially desert-like.

biomes

Biomes

Rules of Rivers

Streams flow into rivers
Most rivers flow from mountains to ocean
Rivers do not cut across continents
Lakes are low points in a river with only one outflow

Learn more about rules of rivers >>

rivers

Mountain Ranges and Climate Barriers:

Mountains as Barriers: Use mountain ranges as climate dividers. Mountains impact how air moves, forcing it to rise and cool, leading to precipitation on one side, and creating dry regions on the leeward side. This explains why deserts often form on the leeward side of mountain ranges (e.g., the rain shadow effect seen in the Himalayas creating the Tibetan Plateau).
Mountains Near the Equator: Include cloud forests or high-altitude rainforests if you have mountain ranges near the equator. Mountains in these areas receive plenty of rain due to the moisture-laden air.

Ocean Currents:

Ocean Currents and Coastal Biomes: Warm ocean currents bring moisture and warmer temperatures to coastal areas, which could result in temperate rainforests or fertile coastal plains. Cold ocean currents make coastal areas drier, contributing to coastal deserts (e.g., the Atacama Desert).
Place temperate rainforests in coastal areas where warm ocean currents bring heavy rainfall, typically on the western edges of continents (like the Pacific Northwest).

Climate Zones Symmetry:

Symmetry Around the Equator: Maintain some symmetry in biomes north and south of the equator. Earth’s Hadley cells create similar biomes on either side of the equator. For example, you can place savannas just outside tropical rainforests, transitioning into deserts at roughly the same latitude in both hemispheres.

Seasonal Changes:

Tropics and Wet-Dry Seasons: In the tropics near the equator, include wet and dry seasons. Due to the shifting position of the Intertropical Convergence Zone (ITCZ), tropical regions often experience significant seasonal rainfall changes that can impact the plant and animal life.
Mid-Latitude Seasonal Variation: In the temperate regions (around the Ferrel cells), create four distinct seasons—spring, summer, autumn, and winter—because of the tilt of the planet and its impact on sunlight distribution.

Savannas as Transitional Biomes:

Transitional Biomes: Place savannas between the rainforests and deserts. These areas are characterized by seasonal rainfall and serve as transitions between the wetter equatorial regions and the arid deserts at higher latitudes. Savannas should have grasslands with scattered trees

Plate Tectonics

When incorporating plate tectonics into your fantasy world, understanding how tectonic processes create mountain ranges is essential for creating a realistic landscape. Here's a guide on how to place mountain ranges based on plate tectonics and geological processes:

1. Understanding Plate Boundaries

Mountain ranges form primarily at tectonic plate boundaries:

Convergent Boundaries:
- Continental-Continental Collision: Plates collide, crumple, and form tall mountains (e.g., Himalayas).
- Oceanic-Continental Collision: The oceanic plate subducts beneath the continental plate, forming volcanic mountain ranges (e.g., Andes).
Divergent Boundaries: Plates move apart, magma rises, and rift mountain ranges form (e.g., Mid-Atlantic Ridge).
Transform Boundaries: Plates slide past each other, creating fault-block mountains and ridges.

2. Key Processes in Mountain Formation

Subduction: One plate slides under another, forming volcanic arcs.
Crustal Thickening: Colliding plates cause crustal folding and thickening, creating large mountain ranges.
Uplift and Erosion: Tectonic activity can uplift mountains, while erosion shapes and varies the landscape.

3. Placing Mountain Ranges in Your Fantasy World

Convergent Boundaries: Place tall mountains at continental collision zones, often snow-capped. At oceanic-continental zones, add volcanic chains near coasts.
Divergent Boundaries: Include rift mountains in mid-ocean ridges or land-based spreading zones.
Transform Faults: Add small, fragmented fault-block mountains along transform boundaries.

4. Geological Considerations for Mountains

Continental Shelves and Coastal Ranges: Coastal mountains from subduction can serve as natural climate barriers.
Island Arcs: Form chains of volcanic islands above subduction zones, ideal for exotic locations.
Hotspots: Include isolated volcanic peaks formed from magma plumes (e.g., Hawaiian Islands).

5. How Mountain Ranges Affect Your World

Climate and Rainfall: Mountains create rain shadows, leading to lush areas on the windward side and deserts on the leeward side.
Natural Borders: Mountains often serve as natural boundaries between regions, making them strategic barriers.
Travel and Trade: High mountains can hinder travel, necessitating passes or tunnels, useful as settings for conflict or secret pathways.
Volcanic Activity: Volcanic mountains provide fertile soil but pose risks, adding dynamic environmental elements to your world.

6. Practical Steps for Adding Mountain Ranges:

Define Plate Boundaries: Determine the tectonic plates in your fantasy world and identify where they collide (convergent), diverge (divergent), or slide past one another (transform).
Place Major Ranges:
- Add high mountain ranges at convergent boundaries between continental plates.
- Place volcanic mountain ranges on coasts where an oceanic plate is subducting beneath a continental plate.
Incorporate Smaller Features:
- Add rift mountains at divergent boundaries and fault-block ridges along transform faults.
Consider Mountain Influence:
- Think about how each mountain range affects climate, political boundaries, and local cultures.
Label and Detail: Give your mountains names and histories. Mountain ranges are often significant in folklore, culture, and political history, so adding lore will make them feel more integrated into your world.

Step-by Step

Map Making Step by Step

This is the process that I like to think through when I first sketch my maps.

Define Climate Zones Based on Latitude
- Equator: Tropical climates (high temperatures, rainfall).
- 30° Latitude: Deserts (high pressure, dry air).
- Mid-Latitudes: Temperate climates (four seasons).
- Polar Regions: Tundra or polar biomes (cold, minimal vegetation).
Establish Plate Tectonics and Geography
- Define tectonic boundaries and place mountains.
- Mountains create rain shadows, influencing rainfall and biomes.
Determine Wind and Ocean Current Patterns
- Use wind patterns to distribute moisture.
- Warm ocean currents: Temperate rainforests.
- Cold currents: Coastal deserts.
Add Key Geographic Features
- Place mountains, rivers, lakes, valleys.
- River Sins to Avoid on Your Maps >>
- Mountains impact rainfall, rivers create riparian biomes.
Place Major Biomes Based on Environmental Factors
- Tropical Rainforest: Equator.
- Savanna: Between rainforest and desert.
- Desert: 30° latitude or leeward side of mountains.
- Temperate Forest: Mid-latitudes.
- Grassland/Prairie: Temperate regions.
- Tundra: Polar regions.
Consider Altitude and Local Variations
- High altitudes: Alpine biomes.
- Montane forests at lower mountain slopes.
Add Transitions and Mixed Biomes
- Include ecotones between major biomes (e.g., savannas, shrublands).
  - Savanna: Transition between tropical rainforest and desert; scattered trees and grasses.
  - Shrubland: Between temperate forest and grassland; mix of shrubs, small trees, and grasses.
  - Wooded Steppe: Between temperate forest and steppe grassland; scattered trees within open plains.
  - Montane Forest: Between lowland forests and alpine tundra; mixed dense forest and alpine meadows on mountain slopes.
  - Mangrove Swamps: Between coastal saltwater and tropical forest; salt-tolerant mangrove trees in brackish water.
  - Chaparral: Between desert and temperate forest; dense shrubs adapted to hot, dry conditions.
  - Riparian Zone: Between terrestrial biomes and freshwater rivers; increased biodiversity due to water presence.
  - Taiga-Tundra Transition: Between boreal forest and tundra; sparse shrubs as the forest gradually gives way to tundra.
  - Floodplain Wetlands: Between grasslands or forests and river systems; supports species adapted to wet and dry cycles.
  - Forest Edge: Between dense forest and open grasslands; a mix of species benefiting from both environments.
Add Natural Disturbances
- Include wildfires, floods, volcanic activity to shape biomes.
Populate Biomes with Flora and Fauna
- Add plants and animals adapted to each biome.
Identify important resources in this region
- Resource abundance or scarcity will drive tensions amongst the intelligent beings who live here
Incorporate Cultural and Societal Elements
- Determine how biomes affect cultures and societies
  1. Forest biomes may have societies that rely on hunting and gathering.
  2. Desert biomes may be home to nomadic tribes that move between oases.
  3. Grasslands may support pastoral or agrarian societies that rely on grazing and crops.