每日吃瓜

Need help to understanding the geologic setting and understanding of how Kanuma and Akadama soils used in bonsai are formed.Are they found in areas other than the Kanuma City area? Are they formed from Mt Akagi deposits (Kanuma Pumice)… or some other origin? Are they waterlain or airfall pumice? Are they formed only in areas above or below ground water table?What van you tell me about these soils in terms of genesis, distribution, etc?

I would think that a forum about geology would render better answers.

But here is a general AI based description that is not reviewed by any geology expert:??

Akadama is a naturally occurring, porous volcanic clay mineral formed?
through the long-term weathering of volcanic ash and tephra deposits, specifically in the Kanto and Tohoku regions of Japan. It is not a mined solid rock, but rather a soft volcanic soil composed largely of amorphous aluminosilicates (like allophane and imogolite) that accumulated over millennia from volcanic activity.?
Here is the geological process of how Akadama formed:

• Volcanic Deposition (Parent Material):?Millions of years ago, repeated eruptions from volcanoes in Japan (notably around Mount Fuji and the Akagi mountain area) deposited massive layers of volcanic ash, pumice, and tephra.
• Weathering and Alteration:?These ash deposits, rich in silica and alumina were subjected to intense weathering in a humid climate. Over time, this natural weathering process transformed the volcanic ash into granular clay minerals, particularly rich in allophane.
• Geothermal Compaction:?Deeper layers of this clay were subjected to heat and pressure from underlying geological activity, which helped "bake" the clay naturally into the firm, granular, reddish-brown, and porous structure (known as "red ball earth") mined today.
• Iron Enrichment:?The reddish-brown color comes from iron oxides?inherent in the volcanic ash, which are enriched during the weathering process.?

Post-Mining Processing
While the material is formed naturally, the Akadama sold for bonsai is excavated from open-cast mines (specifically in Ibaraki Prefecture) and often processed to improve its quality. This includes:?

• Sun-drying and Sifting:?The material is dried and screened for particle size.
• Low-Temperature Firing:?Some high-quality, "hard" Akadama is kiln-fired at roughly 300°C to 900°C to increase its durability, allowing it to withstand water without turning back into mud immediately.?

The key to Akadama's geological uniqueness is its high content of?allophane/imogolite group clay minerals, which provide a very porous, granular structure capable of holding water and oxygen, while buffering nutrients.?