What is true about most higher-grade metallic ores? (1 point)
• They are usually found deep below Earth's surface more than 1,000 ft underground.
• Most of them can be extracted without requiring drilling.
• They are usually found very close to Earth's surface less than 1,000 ft underground.
• Most of them can be extracted using the placer method.
• They are usually found very close to Earth's surface less than 1,000 ft underground.
The correct answer is: They are usually found very close to Earth's surface less than 1,000 ft underground.
The correct answer is: They are usually found very close to Earth's surface less than 1,000 ft underground.
To understand why this is true, let's break down the other options:
- "They are usually found deep below Earth's surface more than 1,000 ft underground": This statement is incorrect. While some metallic ores may be found deep underground, the majority of higher-grade metallic ores are actually found relatively close to the Earth's surface.
- "Most of them can be extracted without requiring drilling": This statement is also incorrect. Extracting metallic ores typically involves various mining methods, including drilling, blasting, and excavation.
- "Most of them can be extracted using the placer method": This statement is not accurate either. The placer method is a mining technique used for recovering valuable minerals from alluvial deposits, which are typically found near rivers, streams, or shorelines. However, higher-grade metallic ores tend to be found in different geological formations and are extracted using different methods.
Therefore, the correct answer is that most higher-grade metallic ores are usually found very close to Earth's surface, generally less than 1,000 ft underground.