How Earth Recycled a Mountain Range

TL;DR

The Adirondack Mountains in New York are made up of billion-year-old igneous rock called anorthosite, which surfaced in the past five million years due to natural mechanisms that are still occurring today.

Transcript

Thanks to Brilliant for supporting this episode of SciShow. Go to Brilliant.orgSciShow to learn how you can take your STEM skills to the next level! [ intro ] Geology really loves its layers. Older stuff on the bottom, newer stuff on top. That is, until this planet of ours cooks, flips, and smushes those rocks every which way. Sometimes super-ancie... Read More

Key Insights

• 🔊 The high peaks of the Adirondack Mountains in New York are composed of billion-year-old anorthosite rock.
• 🫤 These mountains are relatively young, forming only five million years ago.
• 🫤 The formation of the Adirondacks resulted from the Grenville Orogeny event a billion years ago, where anorthosite rock was squeezed up from deep within the Earth's mantle.
• 😘 The Adirondack Mountains continue to rise at a rate of two to three millimeters per year due to the ongoing movement of low-density rock and expansion from heat.
• 👨‍🎤 The rock that makes up the Adirondacks is harder than the newer sediments surrounding it, causing the sediments to erode away over time and expose the ancient rock.
• 🥶 The Adirondacks are a good example of how old rock can resurface and form new mountains through natural processes.
• 💁 The Adirondacks' geology challenges traditional ideas of how mountains form and requires problem-solving to understand the unique mechanisms behind their creation.

Questions & Answers

Q: How old is the rock that makes up the Adirondack Mountains?

The rock on the high peaks of the Adirondacks is approximately one billion years old, making it much older than the mountains themselves.

Q: How did the anorthosite rock surface to form the Adirondack Mountains?

The rock surfaced due to the movement of low-density, buoyant rock from below, filling cracks and expanding to push everything above it up, creating the mountains.

Q: Why are the Adirondack Mountains made up of anorthosite rock?

Anorthosite rock is a type of igneous rock that forms deep underground under extreme conditions, such as when two continental plates collide, which happened during the Grenville Orogeny event a billion years ago.

Q: Why is the Adirondack Mountains rising at a rate of two to three millimeters per year?

The mountains are still rising due to ongoing movements of low-density rock and the expansion caused by heat, with these mechanisms gradually pushing the mountains higher over time.

Summary & Key Takeaways

• The Adirondack Mountains in New York contain rare billion-year-old anorthosite rock.

• These mountains formed only five million years ago, while the rock itself is much older.

• The Adirondacks were formed through the upward movement of low-density rock and expansion due to heat, with these mechanisms still active, causing the mountains to rise at a rate of two to three millimeters per year.