Assume that the east coast of South America and the west coast of Africa are separated by an average distance of \(4,500 \mathrm{km}\) Assume also that GPS measurements indicate that these continents are now moving apart at a rate of \(3.75 \mathrm{cm} / \mathrm{yr}\). If this rate has been constant over geological time, how long ago were these two continents joined together as part of a supercontinent?

The science of plate tectonics explains how the Earth's lithosphere (outer shell) is divided into several plates that glide over the mantle, the semi-solid inner layer. These plates include the continents and ocean floors.

Plate tectonics are responsible for many geological phenomena, including earthquakes, volcanic activity, mountain-building, and the drifting of continents over geological time.
For instance, the exercise shows the east coast of South America and the west coast of Africa moving apart by 3.75 cm/year.

This movement happens because the tectonic plates on which these continents lie are gradually moving away from each other as new crust is formed at divergent boundaries, such as the Mid-Atlantic Ridge.

Understanding plate tectonics helps us study the history of Earth's surface, make predictions about future movements, and assess risks in earthquake-prone areas.

The geological time scale is a system that describes the timing and relationships between events that have occurred throughout Earth's history.

It is divided into eons, eras, periods, and epochs, each marked by significant events, such as mass extinctions or major climatic shifts.

Geologists use this scale to understand not just the age of Earth (about 4.6 billion years), but also the sequence and impact of biological and geological changes.

• The Eon is the largest division of time.
• Each Eon is divided into Eras.
• Eras are subdivided into Periods.
• Periods are divided into Epochs.

In our exercise, the joining time of the continents (1.2 billion years ago) falls in the Proterozoic Eon.
This period is crucial because it represents significant geological activity and the early development of life on Earth.

The geological time scale helps us place events in Earth's history into context and better understand the dynamic processes shaping our planet.

A supercontinent is a massive landmass comprising more than one continental core, or craton, which has merged together over geological time.

Throughout Earth's history, there have been several supercontinents, which have formed and subsequently broken apart due to plate tectonic movements.

The most recent and well-known supercontinent is Pangaea, which began breaking up about 175 million years ago.

• Before Pangaea, other supercontinents like Rodinia and Gondwana existed.
• These formations significantly impacted global climate, sea levels, and biodiversity.
• The breakup of supercontinents leads to the drifting of continents to their current positions.

Concerning the exercise, the calculation shows how the continents of South America and Africa were once part of a supercontinent.
It indicates they began drifting apart approximately 1.2 billion years ago, likely as part of a supercontinent breakup.
Understanding the concept of supercontinents helps geologists trace back the movement of Earth's landmasses and predict future continental shifts.