Not enough sediments in the ocean for an old earth (Talk.Origins)
At current rates of erosion, only thirty million years are needed to account for all the sediments in the ocean. If the earth were as ancient as is claimed, there should be more sediments.
The wording for this claim is not consistent with what Morris says in his book. Among other things he estimates a maximum age of 75 million years not 30 million.
(Talk.Origins quotes in blue)
1. The thickness of sediment in the oceans varies, and it is consistent with the age of the ocean floor. The thickness is zero at the mid-Atlantic Ridge, where new ocean crust is forming, and there is about 150 million years' worth of sediment at the continental margins.
This pattern of thickness does not necessarily indicate differences in the age of the ocean. The same pattern would be a natural result of the run off from the Global flood. Sediment coming off of the continents in this manner would tend to dump more near the continents and with it tapering off as one got further out into the ocean.
The claim that there is "150 million years' worth of sediment at the continental margins," is an estimate of age not depth. This estimation is based on Uniformitarian estimates of the age of the seafloor and as such it is not an independent date. However what Morris shows is that this sediment would have accumulated in only 75 million years at current erosion rates. Simply put, if the Atlantic ocean were really 150 million years old as Talk Origins claims then there should be about twice as much sediment as there actually is.
The average age of the ocean floor is younger than the earth due to subduction at some plate margins and formation of new crust at others.
Fine, because at issue is the maximum age not the average age.
2. The age of the ocean floor can be determined in various ways -- measured via radiometric dating, estimated from the measured rate of seafloor spreading as a result of plate tectonics, and estimated from the ocean depth that predicted from the sea floor sinking as it cools. All these measurements are consistent, and all fit with sediment thickness.
It's no surprise that methods are consistent when they are based on and / or calibrated to one another. For example the above "150 million years' worth of sediment" is clearly not based on erosion rates, but is clearly based on other age estimates of the sea floor.