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Below The Surface | The Formation Of The U S Virgin Islands And British Virgin Islands

Uncovering the journey of the creation of St. Thomas, St. John and the BVI

Nestled in the heart of the Caribbean, the islands of St. Thomas, St. John (both part of the U.S. Virgin Islands), and the British Virgin Islands (BVI) are renowned for their breathtaking beauty, pristine beaches and vibrant marine life.

We spend so much time immersing ourselves in the natural beauty of our islands above the water while cruising along on a powerboat charter or sailing catamaran adventure and just below the surface snorkeling with the magnificent marine life. But we seldom take the time to think about the geological makeup of our islands. Deep beneath the surface lies a captivating tale of volcanic activity that shaped these island chains. Touching on the very surface of their makeup, we’ve put together a history, uncovering the journey of the creation of St. Thomas, St. John and the BVI.

St Thomas Barrier Islands from St John

View of St Thomas Barrier Islands of Lovango Cay, Mingo Cay, Grass Cay, and Thatch Cay from St John

Just touching on the very surface, we’ve put together the history, uncovering the journey of the creation of St. Thomas, St. John and the BVI.

A Hotspot of Volcanic Activity:*

The islands of St. Thomas, St. John, and the BVI owe their existence to volcanic activity that occurred millions of years ago. *Note: There are no active volcanoes located near the northern edge of the Caribbean Plate, where St. Thomas, St. John and the British Virgin Islands are located.

Submarine Volcanism:

The birth of the island chain, including St. Thomas, St. John and the British Virgin Islands began deep beneath the ocean’s surface. Powerful eruptions from underwater volcanoes propelled molten rock, or magma, to the surface. These volcanic eruptions took place repeatedly over a vast period of time, layering the ocean floor with lava and volcanic debris.

Plate Tectonics at Work:

The Caribbean Plate colliding with the North American Plate resulted in the subduction of the North American Plate beneath the Caribbean Plate. As the North American Plate sank into the Earth’s mantle, intense heat and pressure caused the melting of rocks, generating magma that eventually rose to the surface.

Shield Volcanoes: Formed islands like St. Thomas and St. John

The primary type of volcano that formed the islands in our region is known as a shield volcano. Shield volcanoes have broad, gently sloping sides due to the low viscosity of the magma, which allows it to flow easily. As successive eruptions occurred, layers of lava built up, forming the large, shield-shaped islands of St. Thomas and St. John.

Formation of the British Virgin Islands:

The BVI, located just east of St. Thomas and St. John, also emerged from volcanic activity. These volcanic islands were formed through similar processes of magma rising to the surface and subsequent eruptions.

Coral Reefs and Calm Waters of Today:

While volcanic activity shaped the initial landforms, coral reefs played a vital role in shaping the present-day appearance of St. Thomas, St. John and the BVI. Over time, coral colonies grew and developed intricate reef systems, providing habitat for diverse marine life. The reefs also act as a natural barrier, creating calm, turquoise waters ideal for snorkeling, diving and boating.

Book your USVI boat charter or BVI boat charter for a snorkeling adventure and explore today’s coral reefs. 

St. Thomas, St. John, and the BVI possess a rich geological history that spans millions of years. Through the interplay of tectonic forces, volcanic eruptions and the intricate workings of nature, these islands have emerged as Caribbean treasures. Whether you’re strolling along our stunning beaches or immersing yourself in the vibrant marine ecosystems, appreciate the incredible geological origins that birthed these island chains and welcome to the VI.




June 30, 2023

From $130

Snorkel and explore colorful coral reefs full of tropical fish, swim with turtles then visit one of the prettiest beaches in the USVI. On this intimate, semi-private boat charter, up to 12 guests will enjoy a 4-hour snorkel and beach adventure to St. John. This USVI boat charter is a great way to enjoy a day on the water from St. Thomas.

Depart on this St. Thomas boat charter from Red Hook, St. Thomas.

  • Best Family Value
From $1495 $1295

Experience a full day of sailing, snorkeling and beach hopping on a private boat charter. This full-day private boat charter is ideal for up to 8 guests who will enjoy the comfort and amenities aboard a Gemini Legacy catamaran. For groups larger than 8 guests, please call.

Depart on this USVI boat charter from Red Hook, St. Thomas, Cruz Bay, St. John or Lovango Resort and Beach Club.

  • Most Popular
From $1195

Enjoy a private luxury catamaran boat excursion and discover the beautiful, quiet beaches of St. Thomas. Snorkel with stunning coral reefs full of fish and turtles. This boat charter is the perfect way to spend a day on the water in St. Thomas! Private boat charter for up to 12 guests.

Depart on this St. Thomas boat charter from Havensight, St. Thomas—conveniently located near the cruise ship docks.