Question

Which of the following is an example of a detrital sedimentary rock? A) limestone C) breccia B) evaporite D) chalk

Short answer

Breccia is the detrital sedimentary rock.

Step-by-step solution

Understand the Key Characteristics

Detrital (or clastic) sedimentary rocks are composed of minerals or rock fragments derived from pre-existing rocks that have been physically weathered (broken down into fragments) and transported. These typically include rocks like conglomerates, sandstones, and mudstones, and are classified based on the grain size of their particles.

Analyze Each Option

Let's analyze each option to determine if it meets the criteria of a detrital sedimentary rock. A) Limestone: This is a chemical sedimentary rock, often formed from the mineral calcite and typically marine sediments like shells and skeletal remains that precipitate directly out of water. B) Evaporite: This type is formed from the evaporation of water, leaving minerals behind, like halite or gypsum. It is also a chemical sedimentary rock. C) Breccia: This rock is composed of angular rock fragments, cemented together, typically indicating a detrital origin. D) Chalk: Also a kind of limestone, it is formed from the calcareous remains of microorganisms like foraminifera. It is a chemical sedimentary rock.

Identify the Correct Answer

By the process of elimination in Step 2, the remaining option that fits the definition of detrital sedimentary rock due to its clastic nature is C) Breccia.

Key concepts

Clastic Sedimentary Rocks

Clastic sedimentary rocks, also known as detrital sedimentary rocks, are quite fascinating. They are formed from fragments of pre-existing rocks that have been weathered, eroded, and then transported by water, wind, or ice. Once these fragments, or clasts, come to rest, they accumulate in layers, compress over time, and harden into rock through processes like compaction and cementation.
You can identify clastic sedimentary rocks by examining their grain size, which can range from large pebbles in conglomerates to fine particles in shales. Some common examples include:

• Conglomerates: Made up of rounded gravel and pebbles cemented together.
• Sandstones: Consisting mainly of sand-sized particles.
• Mudstones: Comprising very fine particles, giving these rocks a smooth texture.
• Breccia: Identifiable by its coarse, angular rock fragments.

Understanding these rocks provides valuable insights into the geological history and the processes that formed them.

Rock Classification

Rock classification is crucial for geologists when studying Earth's history and structure. Rocks are broadly categorized based on their formation processes into three main types: igneous, sedimentary, and metamorphic. Sedimentary rocks are further divided into clastic, chemical, and organic types based on their composition and formation process.

• Clastic Sedimentary Rocks: As discussed, these are formed from weathered fragments of other rocks.
• Chemical Sedimentary Rocks: Formed from mineral precipitation out of a solution, e.g., limestone and evaporites like salt.
• Organic Sedimentary Rocks: Associated with the accumulation and lithification of organic materials, such as coal.

Classifying rocks involves examining their texture, composition, and formation history, enabling geologists to reconstruct past environments and geological events.

Geology Education

Studying geology opens up a world of understanding about Earth’s structure, history, and processes. Geology education encompasses learning about different rock types, their formation, and the dynamic processes they undergo over geologic time. This knowledge is essential not only for scientific discovery but also for practical applications such as resource extraction and environmental management.
Students of geology are encouraged to observe rocks in the field, analyze samples, and understand geological maps. Courses often include laboratory work to study minerals and rock textures. Hands-on experiences, like fieldtrips, are crucial for grasping concepts like sedimentary layering and fossilization.

• Field Observations: Enable students to learn about real-world geological formations.
• Laboratory Studies: Focus on mineral identification and rock classification.
• Research Projects: Involve investigating geological processes and their effects on the Earth's surface.

Through geology education, students gain insight into Earth’s past, helping them make predictions about future geological events.