Ocate volcanic field facts for kids

The Ocate volcanic field (also called the Mora volcanic field) is a special area in northern New Mexico. It is found in the eastern Sangre de Cristo Mountains. This area has many volcanoes that erupted only once.

About 8.12 million years ago, volcanoes in the Ocate area started erupting. Scientists have found evidence of fourteen different eruption times. The most recent eruptions happened around 0.67 to 0.95 million years ago.

What is the Ocate Volcanic Field?

The Ocate volcanic field is a place where many small volcanoes have erupted over a long time. These volcanoes usually erupt only once. This is why it's called a "monogenetic" volcanic field.

Where is the Ocate Volcanic Field Located?

This volcanic field is in the state of New Mexico, in the United States. It sits in the eastern part of the Sangre de Cristo Mountains. You can find it in Mora County.

How Old is the Ocate Volcanic Field?

The volcanoes in this field have been active for a very long time. The oldest eruptions happened about 8.3 million years ago. The most recent ones were about 0.8 million years ago. This means the field has been active for millions of years!

What Kinds of Rocks are Found Here?

The lava that erupted from these volcanoes is mostly a type of rock called alkali olivine basalt. There are also smaller amounts of other rocks. These include basaltic andesite, olivine andesite, and dacite.

How Did These Rocks Form?

The basaltic lavas came from deep inside the Earth, from a layer called the mantle. The other rocks, like andesites and dacites, formed differently. They were made when the basaltic magma cooled and changed. They also mixed with other melted rocks from the Earth's crust.

What is the Jemez Lineament?

The Ocate volcanic field is located along a special line called the Jemez Lineament. This line is a zone where a lot of volcanic activity happens. It stretches all the way from central Arizona to northeastern New Mexico.

Why is the Jemez Lineament Important?

Scientists believe the Jemez Lineament is a weak spot in the Earth's crust and upper mantle. This weakness makes it easier for magma to rise to the surface and cause volcanic eruptions.

How are the Volcanoes Lined Up?

In the eastern part of the Ocate volcanic field, the volcanoes are lined up from east to west. This direction is straight across from the direction of least pressure in the southern Great Plains. In the western part, the volcanoes are not lined up as clearly. This might be because the area has been moving and changing recently.

How Did the Landscape Change Over Time?

The Ocate volcanic field has a very interesting feature. The oldest lava flows are found on the highest flat areas, called mesas. But the youngest lava flows are found at lower elevations. This is the opposite of what you might expect!

Why is the Oldest Lava on Top?

This unusual pattern happened because of a process called reverse stratigraphy. Here's how it worked:

• First, about 8.3 to 5.7 million years ago, old lava flows spread out on a flat plain.
• Then, the entire area was lifted up.
• After the uplift, rivers and streams cut deep canyons into the older lava flows.
• Later, younger lava flows filled these major river canyons.
• When the uplift stopped, the very youngest lava flows spread out on top of the middle-aged flows.

This process created a landscape where the oldest lava flows are now high up, and the newer ones are in the valleys.