STANDARDS
Next Generation Science Standards

• 3-LS3-2: Use evidence to support the explanation that traits can be influenced by the environment.

KEY TERMS AND CONCEPTS

• Lava: Magma that has come up to Earth’s surface
• Magma: Molten rock before it has erupted on Earth’s surface
• Terrain: The physical features of the Earth’s surface
• Basalt: A hard, rocky, volcanic rock
• Mantle plume: Columns of hot, solid rock that rise from the bottom of the mantle, near the Earth’s core; the mantle plume rises through the layers of the mantle and reaches the Earth’s crust, where it then melts and supplies volcanoes in ocean island chains
• Mantle: The mostly solid layer of rock between the Earth’s core and the Earth’s crust
• Core: The very hot, dense center of the Earth
• Tectonic plates: Plates that make up Earth’s crust
• Magma chamber: As the mantle plume rises through the Earth’s crust, it begins to melt and magma rises through the mantle and crust; when the magma is no longer buoyant, it stalls in the upper mantle or crust, creating a magma chamber

PRIOR KNOWLEDGE AND SKILLS

• Virtual Galápagos Tortoise 101 (Unit 1)

ADVANCE PREP FOR TEACHER KNOWLEDGE
The Galápagos Islands are volcanic islands formed from a mantle plume. The outer shell of the Earth is covered in rigid plates (“tectonic plates”), much like the shell on an egg. The tectonic plates move slowly and continuously all the time, around the planet. The Galápagos are located on a tectonic plate called the Nazca Plate, in the eastern Pacific.

A mantle plume is a column of hot, solid rock that rises from the bottom of the mantle, near the Earth’s core, through the mantle; it rises because it is buoyant, owing to its high temperature, much like a hot air balloon. Once it reaches the Earth’s crust, it begins to melt and the magma, which is less dense and more buoyant than the plan, continues to migrate upward through the crust. Eventually the magma cannot rise anymore and stalls in the crust, a few kilometers below the surface, forming a magma chamber.

In the magma chamber, melted rock (magma) accumulates, building pressure that pushes against the crust. When enough pressure accumulates, the magma will break the overlying crust and erupt onto the surface, in the form of a volcano.

The mantle plume is stationary, but tectonic plates are constantly moving over the magma plume. As the tectonic plate moves away from the mantle plume, the volcano is removed from its magma source and gradually goes extinct. A new volcano takes its place over the mantle plume, like a conveyor belt. There’s now a chain of volcanoes; the volcanoes furthest from the mantle plume are the oldest ones, and those closest to the mantle plume are the youngest volcanoes. In the Galápagos, the Nazca Plate is moving to the east, so the western islands are the youngest islands. They are rocky with little vegetation and no soil, whereas the eastern islands are the oldest islands, where rock has weathered to soil and can support much more vegetation, and where islands have been more eroded by wind, rain, and wave action.