Question

About how fast do plates move? A. a few millimeters each year B. a few centimeters each year c. a few meters each year D. a few kilometers each year

Short answer

B. a few centimeters each year

Step-by-step solution

Understanding Plate Tectonics

Plate tectonics is the theory explaining the movement of the earth's lithosphere which is divided into plates. These plates float on the semi-fluid layer of the mantle below them and move slowly over time due to convection currents.

Identifying Typical Plate Movement Speed

The speed of tectonic plates is measured in terms of how far they move over the course of a year. Scientists have initially measured these speeds using GPS and other methods over many years.

Analyzing Options

Consider each option based on what you know about tectonic plate movement. Tectonic plates move slowly compared to everyday human experiences.

Selecting the Most Common Measurement

Based on scientific measurements, tectonic plates typically move at a rate of a few centimeters per year. This is supported by long-term observations and data collection.

Key concepts

Tectonic Plate Movement

Tectonic plate movement is a fundamental concept in understanding geology. These plates are massive slabs of rock that make up the earth's lithosphere. They move over the planet's surface, and although this movement is slow, it has profound effects. On average, tectonic plates move at a speed of a few centimeters per year. This might seem negligible, but over millions of years, these movements can result in significant changes in the earth's surface. For instance, the formation of mountains, earthquakes, and the drifting of continents are all results of tectonic plate movement.

• Plates move over the semi-fluid mantle.
• Their movement is measured in centimeters per year.
• They are responsible for major geological events.

Lithosphere

The lithosphere is the outer layer of the Earth. It consists of the crust and the uppermost part of the mantle and is divided into tectonic plates. The lithosphere is relatively rigid and sits atop the more fluid asthenosphere, a portion of the mantle that allows the lithosphere to move. This rigid outer shell is important as it interacts with different geological processes like volcanic activity and seismic events. The thickness of the lithosphere can vary, but it generally extends to about 100 kilometers beneath the Earth's surface.

• It includes both the crust and part of the upper mantle.
• It is broken into tectonic plates.
• It interacts with the more fluid asthenosphere below.

Convection Currents

Convection currents are crucial for the movement of tectonic plates. These currents occur in the mantle, driven by the heat from the earth's core. As hot material from deeper within the mantle rises towards the lithosphere, it cools down, and then sinks back towards the core, creating a continuous cycle. This movement of material helps to drag the tectonic plates along the surface of the Earth, albeit slowly. Without convection currents, the dynamic movement of plates would not be possible.

• Caused by heat from the Earth's core.
• Drive the movement of tectonic plates.
• Involves a cycle of rising and sinking material.

Mantle

The mantle is the layer of rock located beneath the Earth's crust. It is composed mainly of silicate minerals and extends down to about 2,900 kilometers. The mantle is divided into the upper mantle and the lower mantle, and it plays a crucial role in plate tectonics due to the convection currents that occur within it. The upper part of the mantle, including the asthenosphere, is semi-fluid, allowing the lithosphere to move. The process of mantle convection drives the movement of tectonic plates and is responsible for much of the Earth's geological activity.

• Composed of silicate minerals.
• Divided into upper and lower sections.
• Essential for the process of plate tectonics.