Question

(6) Currently, oceans cover about 71 percent of Earth's surface. This percentage was much higher early in Earth's history. Explain.

Short answer

Early Earth's oceans covered more surface due to less land mass, which increased over time.

Step-by-step solution

Understanding Earth's Early Surface

Early in Earth's history, the surface was largely molten and hot due to constant volcanic activities and impacts from celestial bodies. As the planet began to cool down, water vapor in the atmosphere condensed to form liquid water.

Formation of Vast Ancient Oceans

As the water vapor condensed, it fell as rain, leading to the accumulation of bodies of water on the Earth's surface. The absence of large land masses in the beginning contributed to the higher percentage of Earth's surface being covered by oceans.

Continental Development Over Time

Over billions of years, tectonic activities caused land to rise from the ocean, forming the continents we see today. These processes decreased the ocean coverage as land masses became more prominent.

Key concepts

Continental Development

Continental development is a continuous process that has shaped the Earth for billions of years. In the early stages of Earth's history, the planet was mostly covered by water. However, through the gradual process of tectonic activities, land continued to rise and form the continents. Over millions of years, the Earth's surface cooled and solidified, allowing for the formation of continental crust. Initially, these continental masses were small and dispersed. However, over time, various geological processes such as volcanic activity and mountain building led to their expansion. The emergence and growth of these land masses decreased the overall percentage of the Earth's surface covered by oceans. The process continues today, contributing to the ever-changing landscape of our planet.

Tectonic Activities

Tectonic activities are central to the formation and transformation of the Earth's surface. They are processes that involve the movement of the Earth's lithospheric plates. These activities have been instrumental in creating continents and ocean basins over geological time scales. Some key tectonic activities include:

• Plate Movements: Tectonic plates can collide, pull apart, or slide against each other. These movements can lead to the formation of mountains, earthquakes, and volcanic activity.
• Subduction Zones: This occurs when one plate moves under another, often leading to volcanic eruptions and the creation of new land.
• Seafloor Spreading: New oceanic crust is formed when plates move apart, which can also affect ocean coverage.

These activities have played a pivotal role in shaping the modern Earth and contributed significantly to the distribution of oceans and continents.

Earth's Surface History

The history of Earth’s surface is a complex tapestry of dramatic changes and transformations. In the very beginning, the planet's surface was almost entirely fluid and volatile. The first major surface change came as volcanic activity and cometary impacts contributed water vapor to the early atmosphere. As the Earth cooled sufficiently, this vapor began to form liquid water, eventually leading to the creation of the vast primordial oceans. As tectonic activities commenced, they influenced the formation of land masses and altered the distribution of water on the planet. Through eons, processes like erosion, sedimentation, and weathering further sculpted these landscapes, continually reshaping Earth's surface. Understanding Earth’s surface history helps us appreciate the dynamic nature of our planet and the mechanisms that have sculpted its present form.