How Do You Know The Earth Is Olders Than 6,00 Years Old

I know that the Earth is more than 6,000 years old from the slide show I watched because of the layers of the cliffs.  The layers of the cliffs look quite large and I know from prior knowledge that the larger the layer, the longer the layer took to grow.  Also, another way I know that the Earth is more than 6,000 years old is because of the depth.  The Earth just did not look like that.  It took time for all of the lower sections of the canyon to deteriorate.  It deteriorated over time because of the elements it endured.  That is how I know that the Earth is more than 6,000 years old from watching the slide show.