Powers Caldera facts for kids

The Powers Caldera is a very old, hidden caldera (a large bowl-shaped hollow) at the top of the Kīlauea volcano. Kīlauea is located on the Big Island of Hawaii. This ancient caldera came before the smaller Kīlauea Caldera we see today. It formed about 2,200 years ago. This happened because of very strong phreatomagmatic eruptions. These are explosive eruptions that happen when hot magma mixes with water.

These powerful explosive eruptions continued for about 1,200 years. During this time, a layer of ash called the Uwēkahuna Ash Member was laid down. Between 850 and 950 CE, the most powerful eruption happened. It threw rocks weighing 9.7 kg (about 21 pounds) at least 4.8 km (3 miles) from the top of the volcano. Even golf ball-sized rocks fell 17.7 km (11 miles) away at the coast!

About 1,000 years ago, effusive eruptions started. These are eruptions where lava flows out gently, instead of exploding. This lava began to fill the Powers Caldera. This marked the end of the 1,200-year period of explosive eruptions. The lava completely filled the Powers Caldera. It even flowed over its edges, making the structure solid.

After this, from 1000 to 1500 CE, a lot of lava flowed through lava tubes. This included the big ʻAilāʻau eruption. The smaller, modern Kīlauea Caldera formed inside the buried Powers Caldera around 1470 CE.

What is the Powers Caldera?

A caldera is a large, bowl-shaped hole that forms when the ground above a volcano's magma chamber collapses. The Powers Caldera is special because it's "buried." This means it's covered by newer lava flows and ash. It's not easily seen today.

How Do We Know It Exists?

Scientists found clues that show the Powers Caldera was once there.

• Ash Layers: They found a fault scarp (a step in the ground caused by a fault) covered by the Uwēkahuna Ash Member. This was found in a place called Uwēkahuna Bluff.
• Ash at Different Heights: The Uwēkahuna Ash Member was also found inside the modern Kīlauea Caldera wall. It was more than 100 meters (330 feet) lower than where it was found near the Tree Molds. This difference in height suggests there was a very large dip or hole at the top of Kīlauea before the ash fell.
• Fault Lines: Scientists also looked at circular cracks and faults in the ground. These are about 2 km (1.2 miles) outside the edge of the modern Kīlauea Caldera. By connecting these lines, they could guess where the edges of the Powers Caldera were.

Scientists believe the Powers Caldera was at least 619 meters (2,030 feet) deep. That's taller than many skyscrapers!

Who Was Howard A. Powers?

The Powers Caldera is named after a person named Howard A. Powers. In 1948, he carefully studied the Uwēkahuna Ash Member. From his studies, he figured out that this large, ancient caldera must have existed.