Question

This image shows lava at a temperature of about \(1200^{\circ} \mathrm{C}\) erupting on the seafloor west of the Tonga trench. What name is given to lava flows like these that erupt underwater?

Short answer

These underwater lava flows are called 'pillow lava'.

Step-by-step solution

Identify the context

The problem is asking for the name given to specific lava flows. These kinds occur underwater, as mentioned in the context.

Recall geological terms

Think about different terms used in geology for various types of lava flows, both on land and underwater.

Connect characteristics

Underwater lava flows are typically associated with specific features or names. The temperature provided suggests very hot lava, typical of volcanic activity.

Name the volcanic feature

Lava flows underwater are often called 'pillow lava' due to their distinct shape and formation process as the lava cools rapidly upon contact with water. Pillows of lava are found near mid-ocean ridges and other underwater volcanic sites.

Key concepts

Underwater Volcanic Activity

When we talk about underwater volcanic activity, we're exploring a fascinating world beneath the ocean's surface. This activity occurs when magma from beneath the Earth's crust erupts through openings in the ocean floor. As opposed to terrestrial volcanoes, underwater volcanic activity happens mostly unknowingly to us, deep in the ocean where the Earth's tectonic plates meet.

These underwater eruptions contribute to the formation of new crust on the ocean floor. When the hot magma is released into the cold water, it cools rapidly and solidifies, forming new geological features. The rapid cooling forms distinct shapes, like the famous pillow lavas. This process not only shapes the seafloor but also plays crucial roles in the carbon cycle and ocean chemistry.

The presence of underwater volcanic activity is significant because it is responsible for the creation of almost 70% of our planet's crust. It influences habitats for marine life and can even trigger mineral deposits beneficial for various industries.

Lava Flow Types

Lava flows come in various types, primarily distinct in their surface textures and formation processes. Understanding these can help in identifying the lava form under different conditions.

• ʻAʻā lava: Characterized by a rough, jagged surface made from broken lava blocks. This kind of flow is typically slower and less fluid.
• Pāhoehoe lava: Known for its smooth and sometimes ropey texture. It's often more fluid and can flow faster than ʻAʻā due to its lower viscosity.
• Pillow lava: This type is distinctive for its bulbous, pillow-like shape. It forms under water when lava erupts and cools rapidly, creating the characteristic soft, rounded pillows.

Each type of lava flow forms under specific environmental conditions, defining the landscape both underwater and on land. Pillow lava, in particular, is common in deep-sea environments around mid-ocean ridges.

Mid-Ocean Ridges

Mid-ocean ridges are one of the most significant geological features on Earth, forming a continuous underwater mountain range stretching across the globe. These ridges are considered "divergent boundaries" where tectonic plates are moving apart.

As the plates separate, magma rises from the mantle, creating new crust as it cools. It is at these ridges that the phenomenon of seafloor spreading occurs. Pillow lava forms here extensively due to the constant volcanic activity submerged under thousands of feet of water.

Mid-ocean ridges are crucial in understanding the theory of plate tectonics. They illustrate how the Earth's surface is constantly being remade and recycled. Ridges also host ecosystems called hydrothermal vents, which support unique life forms capable of withstanding extreme conditions, away from sunlight.

Geological Terms

Geological terms are keys to understanding the Earth's physical features and processes that shape them. Becoming familiar with these terms helps one grasp the dynamic events like volcanic activities.

• Volcano: A geological structure where magma reaches the Earth's surface.
• Magma: The molten rock beneath the Earth's crust, which becomes lava when it erupts.
• Plate Tectonics: The theory describing the large-scale motion of the Earth's lithosphere.
• Pillow Lava: Bulbous lava formed during underwater eruptions due to rapid cooling.
• Divergent Boundary: The area where two tectonic plates move apart, often found at mid-ocean ridges.

These terms and others build a vocabulary that makes discussing geological phenomena meaningful and precise. Understanding them enhances our ability to comprehend the processes that constantly shape our planet.