The answer is very small crystals
The 3 major mountain ranges in the United States are the Pacific ranges and Rocky Mountains in the west and the Appalachian mountains in the east. The Pacific ranges are on the northwestern coast of the United States. The Rocky Mountains are in the western United States but east of the Pacific ranges. They extend all the way from Canada into Mexico and cover 8 states. The Appalachian Mountains are near the East Coast of the United States. They extend from Canada to Alabama. The main difference between the eastern mountain ranges and the western mountain ranges is their ages and heights. The Appalachian Mountain range is the oldest range in the United States. Because of this, the range has faced weathering and erosion, which has worn the mountains down. The highest peaks in the Appalachians are only 6,000 feet. The ranges in the west are much younger and in some cases still growing. The mountains in the west are much higher than those in the east, with peaks over 14,000 ft.
Answer: They existed for a short span of time.
Explanation:
Index fossils are also referred to as the indicator fossils and they are simply used to define the faunal stages.
Some of the characteristics possessed by the index fossils include:
• geographic distribution that's wide
• short vertical range
• rapid evolutionary trends.
