The sea floor is spreading apart from an oceanic ridge labeled A. The data show the age of rock samples taken from the sea floor on both sides of the rid
Age and Distance of Sea-Floor Rocks from Oceanic Ridge
rocks originated at oceanic rocks originated at oceanic
ridge moving west
ridge moving east
100+
Age (Ma)
+
2,000
1,000
50 Ma
ΝΑ
1,080 km
0
1,000
Distance (km)
oceanic ridge
2,000
• Explain the relationship between the age of the rocks and their distance from the mid-ocean ridge.
• Explain how the age and distance data support the statement that the sea floor is spreading.

Ageologist is working in an area with exposed sedimentary rocks and finds a well exposed sequence of stratified rocks. as he works through a thick sequence of limestone, he sees abundant large clam fossils that produce an interlocking texture suggesting a reef, but within the limestone section these clams disappear and the overlying limestone is made up primarily of fragments of corals. he now moves 50 km away and finds limestones interbedded with shales, and the limestones contain the same clam fossils he had seen previously 50 km away. as he continues through this section, the rocks become entirely limestone, and the clams disappear again with coral fossils above forming a reef structure. he concludes