Yokoate-jima: The Volcanic Geography of a Remote Island
Yokoate-jima is a remote island defined by its dramatic volcanic origins and isolated location. Situated in a strategic maritime position, it lies 42 kilometres (23 nmi) south-southwest of Takarajima and 60 kilometres (32 nmi) northwest of Amami Ōshima.
Key Facts
- Composition: Formed by two distinct stratovolcanoes (composite volcanoes).
- Highest Point: Higashimine reaches an elevation of 494.8 metres.
- Last Activity: Volcanic activity occurred around 1835 ± 30 years.
- Climate: Subtropical with a rainy season from May to September.
- Associated Landmasses: Includes the nearby uninhabited Kaminonejima.
Volcanic Structure and Topography
The island is the result of two smaller stratovolcanoes—volcanoes built up by many layers of hardened lava and tephra. These two peaks define the island's silhouette:
- Higashimine (東峰): Located to the east, this is the taller of the two peaks, reaching a maximum elevation of 494.8 metres (1,623 ft).
- Nishimine (西峰): Located to the west, this peak reaches a maximum elevation of 259 metres (850 ft).
The geological history of these peaks includes volcanic activity dating back to the end of the Edo period, specifically around 1835 ± 30 years. The topography varies significantly between the peaks' interiors and exteriors; while the inside of both calderas (large cauldron-like hollows formed by volcanic collapse) are forested, the outer slopes remain largely barren.
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Climate and Surrounding Islands
Yokoate-jima experiences a subtropical climate. This environment is characterized by a distinct rainy season that spans from May through September, influencing the vegetation found within the island's calderas.
Just 2.4 kilometres (1.3 nmi) to the north lies Kaminonejima (上ノ根島). This uninhabited island is not a separate volcanic system but rather another exposed portion of the caldera rim belonging to the same stratovolcano that formed Yokoate-jima.
| Feature | Higashimine (East) | Nishimine (West) |
|---|---|---|
| Maximum Elevation | 494.8 metres (1,623 ft) | 259 metres (850 ft) |
| Interior Vegetation | Forested | Forested |
| Outer Slope Condition | Barren | Barren |
| Last Known Activity | Circa 1835 ± 30 years |
Frequently Asked Questions
Where is Yokoate-jima located?
It is located 42 kilometres south-southwest of Takarajima and 60 kilometres northwest of Amami Ōshima.
What are the two main peaks of the island?
The island is formed by Higashimine in the east and Nishimine in the west.
When was the last volcanic activity recorded on the island?
The only known volcanic activity occurred toward the end of the Edo period, approximately 1835 ± 30 years.
What is the relationship between Yokoate-jima and Kaminonejima?
Kaminonejima is an uninhabited island located 2.4 kilometres north of Yokoate-jima and is part of the same stratovolcano's caldera rim.
What is the weather like on Yokoate-jima?
The island has a subtropical climate with a rainy season that lasts from May to September.