Last updated: May 29, 2024
Place
Cerro La Jara Stop 6
NPS
So far, you have learned that about 1.2 million years ago, a giant volcanic eruption occurred and created Valles Caldera when the roof of the empty magma chamber collapsed. The material that was erupted (called the Bandelier Tuff) was deposited inside the new hole in the ground and on the surrounding landscape. Shortly after that, molten rock that was still under the caldera floor pushed the ground up to create the resurgent dome, Redondo Peak, that is now ahead of you. The volcanic domes Cerro La Jara – to your right, and South Mountain – to your left, were formed when thick, rhyolitic lava was extruded at the surface through vents and fissures that were located above the ring fracture system.
The volcanic dome, Cerro La Jara, is still to your right. This is a good place to see flow banding in the rocks. The banding looks like layers in the rock and indicates that either different lava textures or different lava composition, or both, made the rocks break down and weather differently.
Imagine a lake, right here where you are standing. Over the hundreds of thousands of years since it was formed, the caldera was sometimes home to a lake, or several lakes. Sediment deposits show that one of the lakes was about 75 feet deep here. The gently sloped mound ahead of you is made of a frothy rock called pumice that was floating on a lake and was left behind when the water broke through a lava dam and drained, leaving the pumice raft behind.
Lake deposits of mud, silt, and sand contain climate indicators such as pollen. Scientists use these to learn about past climates. The climate has changed many times since the creation of Valles Caldera and is changing today. Climate records from the last 100 years show the average yearly temperature in the area is increasing quickly and the average yearly precipitation is decreasing.
Continue on the trail to Stop 7, which is on a high point around the corner where you can see the road and mountains in the distance.
The volcanic dome, Cerro La Jara, is still to your right. This is a good place to see flow banding in the rocks. The banding looks like layers in the rock and indicates that either different lava textures or different lava composition, or both, made the rocks break down and weather differently.
Imagine a lake, right here where you are standing. Over the hundreds of thousands of years since it was formed, the caldera was sometimes home to a lake, or several lakes. Sediment deposits show that one of the lakes was about 75 feet deep here. The gently sloped mound ahead of you is made of a frothy rock called pumice that was floating on a lake and was left behind when the water broke through a lava dam and drained, leaving the pumice raft behind.
Lake deposits of mud, silt, and sand contain climate indicators such as pollen. Scientists use these to learn about past climates. The climate has changed many times since the creation of Valles Caldera and is changing today. Climate records from the last 100 years show the average yearly temperature in the area is increasing quickly and the average yearly precipitation is decreasing.
Continue on the trail to Stop 7, which is on a high point around the corner where you can see the road and mountains in the distance.