Science and the Sea Podcast

<p><img width="2560" height="1440" src="https://utmsi.utexas.edu/wp-content/uploads/2025/12/790325_Tonga-Trench-scaled.jpg" class="attachment-post-thumbnail size-post-thumbnail wp-post-image" alt="" decoding="async" fetchpriority="high" srcset="https://utmsi.utexas.edu/wp-content/uploads/2025/12/790325_Tonga-Trench-scaled.jpg 2560w, https://utmsi.utexas.edu/wp-content/uploads/2025/12/790325_Tonga-Trench-300x169.jpg 300w, https://utmsi.utexas.edu/wp-content/uploads/2025/12/790325_Tonga-Trench-1024x576.jpg 1024w, https://utmsi.utexas.edu/wp-content/uploads/2025/12/790325_Tonga-Trench-360x202.jpg 360w, https://utmsi.utexas.edu/wp-content/uploads/2025/12/790325_Tonga-Trench-768x432.jpg 768w, https://utmsi.utexas.edu/wp-content/uploads/2025/12/790325_Tonga-Trench-1536x864.jpg 1536w, https://utmsi.utexas.edu/wp-content/uploads/2025/12/790325_Tonga-Trench-2048x1152.jpg 2048w" sizes="(max-width: 2560px) 100vw, 2560px" /></p> <p>Second place doesn’t get a lot of attention: the second-tallest mountain, the second expedition to reach the North Pole, silver medalists in the Olympics. The second-deepest spot in the oceans isn’t exactly a household name either: the Tonga Trench.</p> <p>The deepest spot is in the Mariana Trench, in the western Pacific Ocean. It’s about 36,000 feet deep—almost seven miles. That’s a few hundred feet deeper than the lowest spot in the Tonga Trench.</p> <p>The Tonga is in the southern hemisphere, northeast of New Zealand. It’s more than 800 miles long, and runs parallel to the islands of Tonga. Its deepest spot is the Horizon Deep. It’s named for the ship that discovered it back in 1952.</p> <p>The trench is created by the motions of two of the plates that make up Earth’s crust. One plate is plunging below the other. The Tonga Trench is a groove where the descending plate disappears below the other. And the crust along one section of the trench is disappearing faster than at any other spot on Earth—about nine inches per year.           </p> <p>A couple of expeditions have taken a close look at the trench. They found an abundance of life along its steep walls and all the way to the bottom. One thing they didn’t find was evidence of humans. Explorations of the world’s other major trenches have all found trash—even in the deepest parts. But the Tonga Trench is pristine—a top ranking for the second-deepest spot in the oceans.</p> <p>The post <a href="https://utmsi.utexas.edu/science-and-the-sea/radio-program/tonga-trench/">Tonga Trench</a> appeared first on <a href="https://utmsi.utexas.edu">Marine Science Institute. The University of Texas at Austin.</a>.</p>