Match The Type Of Glacial Deposit With Its Correct Characteristics.

Matching Glacial Deposits with Their Characteristics: A Comprehensive Guide

Glacial deposits, also known as glacial drift, are a fascinating testament to the immense power of glaciers. Understanding the different types of these deposits and their unique characteristics is crucial for geologists, geographers, and anyone interested in Earth's history and landscape formation. This article will delve into the various types of glacial deposits, matching each with its key attributes. This will help you understand the processes that shaped our planet and identify these formations in the field.

Types of Glacial Deposits and Their Characteristics

Glaciers sculpt the land through erosion and deposition, leaving behind a wide array of landforms and sediments. These deposits can be broadly categorized into two main groups: till and outwash. Let's explore each in detail:

1. Till: Unsorted and Unstratified Deposits

Till is a characteristic glacial deposit composed of a heterogeneous mixture of sediment sizes, ranging from clay-sized particles to enormous boulders. Its defining characteristics are:

• Unsorted: Till lacks any discernible size grading or sorting. This is because glacial movement doesn't allow for the segregation of particles based on size, unlike water-borne sediments. You'll find clays, sands, gravels, and boulders all jumbled together.
• Unstratified: Till shows no layering or bedding. The chaotic deposition by the glacier prevents the formation of distinct layers.
• Angular to Subangular Clasts: The rock fragments within till often have sharp edges and corners, indicating minimal transport and abrasion.
• Presence of Glacial Erratics: Large boulders (glacial erratics) that are vastly different in composition from the surrounding bedrock are a common feature of till deposits. These erratics were transported long distances by the glacier from their source area.
• Formation: Till is deposited directly by the glacier itself, either through melting or deposition at the glacier's terminus (end). Examples include moraines, which are ridges of till deposited at the glacier's edge.

2. Outwash: Sorted and Stratified Deposits

Outwash, in contrast to till, is composed of sediments transported and deposited by meltwater streams flowing from a glacier. This leads to distinctly different characteristics:

• Sorted: The sediments in outwash are sorted by size and weight due to the action of flowing water. Larger, heavier particles are deposited closer to the glacier's edge, while finer particles are carried further downstream.
• Stratified: Outwash displays distinct layers or bedding due to variations in sediment size and depositional processes. These layers reflect changes in water flow or sediment supply.
• Rounded Clasts: The clasts (fragments of rock) in outwash tend to be more rounded and smoothed compared to those in till, due to abrasion during transport by water.
• Formation: Outwash plains and kames are common landforms formed by outwash deposits. Outwash plains are broad, flat areas composed of stratified sand and gravel, while kames are mounds or hills formed by sediment deposition within ice-walled channels.

Other Glacial Deposits:

Beyond till and outwash, other important glacial deposits include:

• Glacial Lake Sediments: These deposits are formed in lakes that accumulate behind glaciers or in depressions carved by glacial activity. They often consist of finely laminated clays and silts, sometimes with varves (annual layers).
• Glaciofluvial Deposits: A broader term encompassing sediments deposited by glacial meltwater, including outwash and other related features.
• Glaciolacustrine Deposits: Sediments deposited in glacial lakes, often displaying fine layering and varves.

Understanding the differences between till and outwash, along with other glacial deposits, provides invaluable insight into the dynamics of past glaciations and the powerful forces that shape our landscapes. By carefully observing the characteristics of a deposit—its sorting, stratification, clast shape, and composition—we can accurately identify its glacial origin and learn more about the environmental conditions during the time of its formation.