【Japanese Pottery】Conditions for Large Clay Deposits

Table of Contents

• 1.Why Are There Many Pottery-Producing Regions in Japan?
• 2.How Clay Accumulates
• 3.Common Features of Pottery-Producing Regions
• 4.Conclusion: Nature’s Role in Clay Formation

1. Why Are There Many Pottery-Producing Regions in Japan?

Japan has numerous renowned ceramic production areas with high-quality refractory clay and massive clay deposits.
What natural conditions contribute to the accumulation of such vast amounts of clay in these regions?

2. How Clay Accumulates

Clay originates from weathered granite and other rocks (see previous article: How Clay Forms). Initially, the weathered material settles on the surface in tiny amounts. However, certain natural conditions allow these small particles to concentrate into large deposits.
1.Erosion and Water Flow
　・Rainfall washes fine clay particles from granite-rich areas.
　・Some material seeps into the ground, while the rest flows downhill into rivers.
　・Clay particles carried by rivers settle in slow-moving sections.
2.Natural Traps for Clay Accumulation
　・In river basins, clay accumulates in areas where water slows down (e.g., bends, floodplains, or deltas).
　・If cracks or depressions exist in the ground, clay can settle there before reaching a river.
　・Over time, landslides or erosion may expose buried clay deposits, revealing them accidentally.

Through these geological processes, certain regions develop huge, concentrated clay reserves over thousands to millions of years.

3. Common Features of Pottery-Producing Regions

Understanding how clay accumulates helps predict where large clay deposits are likely to form.
Some ideal locations include:
・Downstream river areas where many tributaries converge.
・Lowland areas within mountainous regions.
・Former lake or swamp beds that have dried up, leaving behind thick sediment layers.
Many of Japan’s famous pottery regions are located near oceans, large lakes, or fertile lowlands, all of which favor clay accumulation.
Examples: Japan’s Six Ancient Kilns (六古窯, Rokkoyō)
The six traditional kiln sites (dating back to medieval Japan) all benefited from their geological surroundings.
Prehistoric Lake Influence

・Seto’s clay originated from a prehistoric lake six times larger than present-day Lake Biwa (approximately 5 million years ago).
・The lake gradually dried up, leaving behind thick, high-quality clay deposits, which led to Seto’s thriving pottery industry.

4. Conclusion: Nature’s Role in Clay Formation

The best pottery regions in Japan owe their success to ancient geological events.
・The clay that potters use today has accumulated over thousands to millions of years.
・Even now, new clay deposits are slowly forming in unknown locations, continuing nature’s cycle.
Understanding the natural processes behind clay formation enhances our appreciation of ceramic traditions and the deep connection between geography and craftsmanship.